[Sync] Move //sync to //components/sync.

sync/protocol/sync.proto

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-//
-// Sync protocol for communication between sync client and server.
-
-// Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
-// any fields in this file.
-
-syntax = "proto2";
-
-option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
-
-package sync_pb;
-
-import "app_list_specifics.proto";
-import "app_notification_specifics.proto";
-import "app_setting_specifics.proto";
-import "app_specifics.proto";
-import "arc_package_specifics.proto";
-import "article_specifics.proto";
-import "attachments.proto";
-import "autofill_specifics.proto";
-import "bookmark_specifics.proto";
-import "client_commands.proto";
-import "client_debug_info.proto";
-import "device_info_specifics.proto";
-import "dictionary_specifics.proto";
-import "encryption.proto";
-import "experiments_specifics.proto";
-import "extension_setting_specifics.proto";
-import "extension_specifics.proto";
-import "favicon_image_specifics.proto";
-import "favicon_tracking_specifics.proto";
-import "get_updates_caller_info.proto";
-import "history_delete_directive_specifics.proto";
-import "nigori_specifics.proto";
-import "managed_user_setting_specifics.proto";
-import "managed_user_shared_setting_specifics.proto";
-import "managed_user_specifics.proto";
-import "managed_user_whitelist_specifics.proto";
-import "password_specifics.proto";
-import "preference_specifics.proto";
-import "priority_preference_specifics.proto";
-import "search_engine_specifics.proto";
-import "session_specifics.proto";
-import "sync_enums.proto";
-import "synced_notification_app_info_specifics.proto";
-import "synced_notification_specifics.proto";
-import "theme_specifics.proto";
-import "typed_url_specifics.proto";
-import "unique_position.proto";
-import "wifi_credential_specifics.proto";
-
-// Used for inspecting how long we spent performing operations in different
-// backends. All times must be in millis.
-message ProfilingData {
-  optional int64 meta_data_write_time = 1;
-  optional int64 file_data_write_time = 2;
-  optional int64 user_lookup_time = 3;
-  optional int64 meta_data_read_time = 4;
-  optional int64 file_data_read_time = 5;
-  optional int64 total_request_time = 6;
-}
-
-message EntitySpecifics {
-  // If a datatype is encrypted, this field will contain the encrypted
-  // original EntitySpecifics. The extension for the datatype will continue
-  // to exist, but contain only the default values.
-  // Note that currently passwords employ their own legacy encryption scheme and
-  // do not use this field.
-  optional EncryptedData encrypted = 1;
-
-  // To add new datatype-specific fields to the protocol, extend
-  // EntitySpecifics.  First, pick a non-colliding tag number by
-  // picking a Cr-Commit-Position of one of your past commits
-  // to src.chromium.org.  Then, in a different protocol buffer
-  // definition, define your message type, and add an optional field
-  // to the list below using the unique tag value you selected.
-  //
-  //  optional MyDatatypeSpecifics my_datatype = 32222;
-  //
-  // where:
-  //   - 32222 is the non-colliding tag number you picked earlier.
-  //   - MyDatatypeSpecifics is the type (probably a message type defined
-  //     in your new .proto file) that you want to associate with each
-  //     object of the new datatype.
-  //   - my_datatype is the field identifier you'll use to access the
-  //     datatype specifics from the code.
-  //
-  // Server implementations are obligated to preserve the contents of
-  // EntitySpecifics when it contains unrecognized fields.  In this
-  // way, it is possible to add new datatype fields without having
-  // to update the server.
-  //
-  // Note: The tag selection process is based on legacy versions of the
-  // protocol which used protobuf extensions. We have kept the process
-  // consistent as the old values cannot change.  The 5+ digit nature of the
-  // tags also makes them recognizable (individually and collectively) from
-  // noise in logs and debugging contexts, and creating a divergent subset of
-  // tags would only make things a bit more confusing.
-
-  optional AutofillSpecifics autofill = 31729;
-  optional BookmarkSpecifics bookmark = 32904;
-  optional PreferenceSpecifics preference = 37702;
-  optional TypedUrlSpecifics typed_url = 40781;
-  optional ThemeSpecifics theme = 41210;
-  optional AppNotification app_notification = 45184;
-  optional PasswordSpecifics password = 45873;
-  optional NigoriSpecifics nigori = 47745;
-  optional ExtensionSpecifics extension = 48119;
-  optional AppSpecifics app = 48364;
-  optional SessionSpecifics session = 50119;
-  optional AutofillProfileSpecifics autofill_profile = 63951;
-  optional SearchEngineSpecifics search_engine = 88610;
-  optional ExtensionSettingSpecifics extension_setting = 96159;
-  optional AppSettingSpecifics app_setting = 103656;
-  optional HistoryDeleteDirectiveSpecifics history_delete_directive = 150251;
-  optional SyncedNotificationSpecifics synced_notification = 153108;
-  optional SyncedNotificationAppInfoSpecifics synced_notification_app_info = 235816;
-  optional DeviceInfoSpecifics device_info = 154522;
-  optional ExperimentsSpecifics experiments = 161496;
-  optional PriorityPreferenceSpecifics priority_preference = 163425;
-  optional DictionarySpecifics dictionary = 170540;
-  optional FaviconTrackingSpecifics favicon_tracking = 181534;
-  optional FaviconImageSpecifics favicon_image = 182019;
-  optional ManagedUserSettingSpecifics managed_user_setting = 186662;
-  optional ManagedUserSpecifics managed_user = 194582;
-  optional ManagedUserSharedSettingSpecifics managed_user_shared_setting =
-      202026;
-  optional ManagedUserWhitelistSpecifics managed_user_whitelist = 306060;
-  optional ArticleSpecifics article = 223759;
-  optional AppListSpecifics app_list = 229170;
-  optional WifiCredentialSpecifics wifi_credential = 218175;
-  optional AutofillWalletSpecifics autofill_wallet = 306270;
-  optional WalletMetadataSpecifics wallet_metadata = 330441;
-  optional ArcPackageSpecifics arc_package = 340906;
-}
-
-message SyncEntity {
-  // This item's identifier.  In a commit of a new item, this will be a
-  // client-generated ID.  If the commit succeeds, the server will generate
-  // a globally unique ID and return it to the committing client in the
-  // CommitResponse.EntryResponse.  In the context of a GetUpdatesResponse,
-  // |id_string| is always the server generated ID.  The original
-  // client-generated ID is preserved in the |originator_client_id| field.
-  // Present in both GetUpdatesResponse and CommitMessage.
-  optional string id_string = 1;
-
-  // An id referencing this item's parent in the hierarchy.  In a
-  // CommitMessage, it is accepted for this to be a client-generated temporary
-  // ID if there was a new created item with that ID appearing earlier
-  // in the message.  In all other situations, it is a server ID.
-  // Present in both GetUpdatesResponse and CommitMessage.
-  optional string parent_id_string = 2;
-
-  // old_parent_id is only set in commits and indicates the old server
-  // parent(s) to remove. When omitted, the old parent is the same as
-  // the new.
-  // Present only in CommitMessage.
-  optional string old_parent_id = 3;
-
-  // The version of this item -- a monotonically increasing value that is
-  // maintained by for each item.  If zero in a CommitMessage, the server
-  // will interpret this entity as a newly-created item and generate a
-  // new server ID and an initial version number.  If nonzero in a
-  // CommitMessage, this item is treated as an update to an existing item, and
-  // the server will use |id_string| to locate the item.  Then, if the item's
-  // current version on the server does not match |version|, the commit will
-  // fail for that item.  The server will not update it, and will return
-  // a result code of CONFLICT.  In a GetUpdatesResponse, |version| is
-  // always positive and indentifies the revision of the item data being sent
-  // to the client.
-  // Present in both GetUpdatesResponse and CommitMessage.
-  required int64 version = 4;
-
-  // Last modification time (in java time milliseconds)
-  // Present in both GetUpdatesResponse and CommitMessage.
-  optional int64 mtime = 5;
-
-  // Creation time.
-  // Present in both GetUpdatesResponse and CommitMessage.
-  optional int64 ctime = 6;
-
-  // The name of this item.
-  // Historical note:
-  //   Since November 2010, this value is no different from non_unique_name.
-  //   Before then, server implementations would maintain a unique-within-parent
-  //   value separate from its base, "non-unique" value.  Clients had not
-  //   depended on the uniqueness of the property since November 2009; it was
-  //   removed from Chromium by http://codereview.chromium.org/371029 .
-  // Present in both GetUpdatesResponse and CommitMessage.
-  required string name = 7;
-
-  // The name of this item.  Same as |name|.
-  // |non_unique_name| should take precedence over the |name| value if both
-  // are supplied.  For efficiency, clients and servers should avoid setting
-  // this redundant value.
-  // Present in both GetUpdatesResponse and CommitMessage.
-  optional string non_unique_name = 8;
-
-  // A value from a monotonically increasing sequence that indicates when
-  // this item was last updated on the server. This is now equivalent
-  // to version. This is now deprecated in favor of version.
-  // Present only in GetUpdatesResponse.
-  optional int64 sync_timestamp = 9;
-
-  // If present, this tag identifies this item as being a uniquely
-  // instanced item.  The server ensures that there is never more
-  // than one entity in a user's store with the same tag value.
-  // This value is used to identify and find e.g. the "Google Chrome" settings
-  // folder without relying on it existing at a particular path, or having
-  // a particular name, in the data store.
-  //
-  // This variant of the tag is created by the server, so clients can't create
-  // an item with a tag using this field.
-  //
-  // Use client_defined_unique_tag if you want to create one from the client.
-  //
-  // An item can't have both a client_defined_unique_tag and
-  // a server_defined_unique_tag.
-  //
-  // Present only in GetUpdatesResponse.
-  optional string server_defined_unique_tag = 10;
-
-  // If this group is present, it implies that this SyncEntity corresponds to
-  // a bookmark or a bookmark folder.
-  //
-  // This group is deprecated; clients should use the bookmark EntitySpecifics
-  // protocol buffer extension instead.
-  optional group BookmarkData = 11 {
-    // We use a required field to differentiate between a bookmark and a
-    // bookmark folder.
-    // Present in both GetUpdatesMessage and CommitMessage.
-    required bool bookmark_folder = 12;
-
-    // For bookmark objects, contains the bookmark's URL.
-    // Present in both GetUpdatesResponse and CommitMessage.
-    optional string bookmark_url = 13;
-
-    // For bookmark objects, contains the bookmark's favicon. The favicon is
-    // represented as a 16X16 PNG image.
-    // Present in both GetUpdatesResponse and CommitMessage.
-    optional bytes bookmark_favicon = 14;
-  }
-
-  // Supplies a numeric position for this item, relative to other items with the
-  // same parent.  Deprecated in M26, though clients are still required to set
-  // it.
-  //
-  // Present in both GetUpdatesResponse and CommitMessage.
-  //
-  // At one point this was used as an alternative / supplement to
-  // the deprecated |insert_after_item_id|, but now it, too, has been
-  // deprecated.
-  //
-  // In order to maintain compatibility with older clients, newer clients should
-  // still set this field.  Its value should be based on the first 8 bytes of
-  // this item's |unique_position|.
-  //
-  // Nerwer clients must also support the receipt of items that contain
-  // |position_in_parent| but no |unique_position|.  They should locally convert
-  // the given int64 position to a UniquePosition.
-  //
-  // The conversion from int64 to UniquePosition is as follows:
-  // The int64 value will have its sign bit flipped then placed in big endian
-  // order as the first 8 bytes of the UniquePosition.  The subsequent bytes of
-  // the UniquePosition will consist of the item's unique suffix.
-  //
-  // Conversion from UniquePosition to int64 reverses this process: the first 8
-  // bytes of the position are to be interpreted as a big endian int64 value
-  // with its sign bit flipped.
-  optional int64 position_in_parent = 15;
-
-  // Contains the ID of the element (under the same parent) after which this
-  // element resides. An empty string indicates that the element is the first
-  // element in the parent.  This value is used during commits to specify
-  // a relative position for a position change.  In the context of
-  // a GetUpdatesMessage, |position_in_parent| is used instead to
-  // communicate position.
-  //
-  // Present only in CommitMessage.
-  //
-  // This is deprecated.  Clients are allowed to omit this as long as they
-  // include |position_in_parent| instead.
-  optional string insert_after_item_id = 16;
-
-  // Arbitrary key/value pairs associated with this item.
-  // Present in both GetUpdatesResponse and CommitMessage.
-  // Deprecated.
-  // optional ExtendedAttributes extended_attributes = 17;
-
-  // If true, indicates that this item has been (or should be) deleted.
-  // Present in both GetUpdatesResponse and CommitMessage.
-  optional bool deleted = 18 [default = false];
-
-  // A GUID that identifies the the sync client who initially committed
-  // this entity.  This value corresponds to |cache_guid| in CommitMessage.
-  // This field, along with |originator_client_item_id|, can be used to
-  // reunite the original with its official committed version in the case
-  // where a client does not receive or process the commit response for
-  // some reason.
-  //
-  // Present only in GetUpdatesResponse.
-  //
-  // This field is also used in determining the unique identifier used in
-  // bookmarks' unique_position field.
-  optional string originator_cache_guid = 19;
-
-  // The local item id of this entry from the client that initially
-  // committed this entity. Typically a negative integer.
-  // Present only in GetUpdatesResponse.
-  //
-  // This field is also used in determinging the unique identifier used in
-  // bookmarks' unique_position field.
-  optional string originator_client_item_id = 20;
-
-  // Extensible container for datatype-specific data.
-  // This became available in version 23 of the protocol.
-  optional EntitySpecifics specifics = 21;
-
-  // Indicate whether this is a folder or not. Available in version 23+.
-  optional bool folder = 22 [default = false];
-
-  // A client defined unique hash for this entity.
-  // Similar to server_defined_unique_tag.
-  //
-  // When initially committing an entity, a client can request that the entity
-  // is unique per that account. To do so, the client should specify a
-  // client_defined_unique_tag. At most one entity per tag value may exist.
-  // per account. The server will enforce uniqueness on this tag
-  // and fail attempts to create duplicates of this tag.
-  // Will be returned in any updates for this entity.
-  //
-  // The difference between server_defined_unique_tag and
-  // client_defined_unique_tag is the creator of the entity. Server defined
-  // tags are entities created by the server at account creation,
-  // while client defined tags are entities created by the client at any time.
-  //
-  // During GetUpdates, a sync entity update will come back with ONE of:
-  // a) Originator and cache id - If client committed the item as non "unique"
-  // b) Server tag - If server committed the item as unique
-  // c) Client tag - If client committed the item as unique
-  //
-  // May be present in CommitMessages for the initial creation of an entity.
-  // If present in Commit updates for the entity, it will be ignored.
-  //
-  // Available in version 24+.
-  //
-  // May be returned in GetUpdatesMessage and sent up in CommitMessage.
-  //
-  optional string client_defined_unique_tag = 23;
-
-  // This positioning system had a relatively short life.  It was made obsolete
-  // by |unique_position| before either the client or server made much of an
-  // attempt to support it.  In fact, no client ever read or set this field.
-  //
-  // Deprecated in M26.
-  optional bytes ordinal_in_parent = 24;
-
-  // This is the fourth attempt at positioning.
-  //
-  // This field is present in both GetUpdatesResponse and CommitMessage, if the
-  // item's type requires it and the client that wrote the item supports it (M26
-  // or higher).  Clients must also be prepared to handle updates from clients
-  // that do not set this field.  See the comments on
-  // |server_position_in_parent| for more information on how this is handled.
-  //
-  // This field will not be set for items whose type ignores positioning.
-  // Clients should not attempt to read this field on the receipt of an item of
-  // a type that ignores positioning.
-  //
-  // Refer to its definition in unique_position.proto for more information about
-  // its internal representation.
-  optional UniquePosition unique_position = 25;
-
-  // Attachment ids of attachments associated with this SyncEntity.
-  repeated AttachmentIdProto attachment_id = 26;
-};
-
-// This message contains diagnostic information used to correlate
-// commit-related traffic with extensions-related mutations to the
-// data models in chromium.  It plays no functional role in
-// processing this CommitMessage.
-message ChromiumExtensionsActivity {
-  // The human-readable ID identifying the extension responsible
-  // for the traffic reported in this ChromiumExtensionsActivity.
-  optional string extension_id = 1;
-
-  // How many times the extension successfully invoked a write
-  // operation through the bookmarks API since the last CommitMessage.
-  optional uint32 bookmark_writes_since_last_commit = 2;
-};
-
-// Client specific configuration information.
-message ClientConfigParams {
-  // The set of data types this client has enabled. Note that this does not
-  // include proxy types, as they do not have protocol field numbers and are
-  // placeholder types that implicitly enable protocol types.
- repeated int32 enabled_type_ids = 1;
-
- // Whether the PROXY_TABS proxy datatype is enabled on this client.
- optional bool tabs_datatype_enabled = 2;
-
- // Whether the account(s) present in the content area's cookie jar match the
- // chrome account. If multiple accounts are present in the cookie jar, a
- // mismatch implies all of them are different from the chrome account.
- optional bool cookie_jar_mismatch = 3;
-};
-
-message CommitMessage {
-  repeated SyncEntity entries = 1;
-
-  // A GUID that identifies the committing sync client.  This value will be
-  // returned as originator_cache_guid for any new items.
-  optional string cache_guid = 2;
-
-  repeated ChromiumExtensionsActivity extensions_activity = 3;
-
-  // The configuration of this client at commit time. Used by the server to
-  // make commit-time decisions about how to process datatypes that might
-  // involve server-side interaction, and e.g require explicit user intent for
-  // syncing a particular data type regardless of whether a commit for that
-  // datatype is currently being sent up.
-  optional ClientConfigParams config_params = 4;
-
-  // Set of optional per-client datatype contexts.
-  repeated DataTypeContext client_contexts = 5;
-};
-
-// This message communicates additional per-type information related to
-// requests with origin GU_TRIGGER.  This message is not relevant when any
-// other origin value is used.
-// Introduced in M29.
-message GetUpdateTriggers {
-  // An opaque-to-the-client string of bytes, received through a notification,
-  // that the server may interpret as a hint about the location of the latest
-  // version of the data for this type.
-  //
-  // Note that this will eventually replace the 'optional' field of the same
-  // name defined in the progress marker, but the client and server should
-  // support both until it's safe to deprecate the old one.
-  //
-  // This field was introduced in M29.
-  repeated string notification_hint = 1;
-
-  // This flag is set if the client was forced to drop hints because the number
-  // of queued hints exceeded its limit.  The oldest hints will be discarded
-  // first.  Introduced in M29.
-  optional bool client_dropped_hints = 2;
-
-  // This flag is set when the client suspects that its list of invalidation
-  // hints may be incomplete.  This may be the case if:
-  // - The client is syncing for the first time.
-  // - The client has just restarted and it was unable to keep track of
-  //   invalidations that were received prior to the restart.
-  // - The client's connection to the invalidation server is currently or
-  //   was recently broken.
-  //
-  // It's difficult to provide more details here.  This is implemented by
-  // setting the flag to false whenever anything that might adversely affect
-  // notifications happens (eg. a crash, restart on a platform that doesn't
-  // support invalidation ack-tracking, transient invalidation error) and is
-  // unset only after we've experienced one successful sync cycle while
-  // notifications were enabled.
-  //
-  // This flag was introduced in M29.
-  optional bool invalidations_out_of_sync = 3;
-
-  // This counts the number of times the syncer has been asked to commit
-  // changes for this type since the last successful sync cycle.  The number of
-  // nudges may not be related to the actual number of items modified.  It
-  // often correlates with the number of user actions, but that's not always
-  // the case.
-  // Introduced in M29.
-  optional int64 local_modification_nudges = 4;
-
-  // This counts the number of times the syncer has been explicitly asked to
-  // fetch updates for this type since the last successful sync cycle.  These
-  // explicit refresh requests should be relatively rare on most platforms, and
-  // associated with user actions.  For example, at the time of this writing
-  // the most common (only?) source of refresh requests is when a user opens
-  // the new tab page on a platform that does not support sessions
-  // invalidations.
-  // Introduced in M29.
-  optional int64 datatype_refresh_nudges = 5;
-
-  // This flag is set if the invalidation server reports that it may have
-  // dropped some invalidations at some point.  Introduced in M33.
-  optional bool server_dropped_hints = 6;
-
-  // This flag is set if this GetUpdate request is due at least in part due
-  // to the fact that this type has not finished initial sync yet, and the
-  // client would like to initialize itself with the server data.
-  //
-  // Only some types support performing an initial sync as part of a normal
-  // GetUpdate request.  Many types must be in configure mode when fetching
-  // initial sync data.
-  //
-  // Introduced in M38.
-  optional bool initial_sync_in_progress = 7;
-
-  // This flag is set if this GetUpdate request is due to client receiving
-  // conflict response from server, so client needs to sync and then resolve
-  // conflict locally, and then commit again.
-  //
-  // Introduced in M42.
-  optional bool sync_for_resolve_conflict_in_progress = 8;
-}
-
-message GarbageCollectionDirective {
-  enum Type {
-    UNKNOWN = 0;
-    VERSION_WATERMARK = 1;
-    AGE_WATERMARK = 2;
-    MAX_ITEM_COUNT = 3;
-  }
-
-  optional Type type = 1 [default = UNKNOWN];
-
-  // This field specifies the watermark for the versions which should get
-  // garbage collected.  The client should purge all sync entities with a
-  // version smaller than version_watermark locally.
-  optional int64 version_watermark = 2;
-
-  // This field specifies the watermark in terms of age in days.  The client
-  // should purge all sync entities which are older than this specific value
-  // based on last modified time.
-  optional int32 age_watermark_in_days = 3;
-
-  // This field specifies the max number of items that the client should keep
-  // for a specific datatype.  If the number of items exceeds this limit, the
-  // client should purge the extra sync entities based on the LRU rule.
-  optional int32 max_number_of_items = 4;
-}
-
-message DataTypeProgressMarker {
-  // An integer identifying the data type whose progress is tracked by this
-  // marker.  The legitimate values of this field correspond to the protobuf
-  // field numbers of all EntitySpecifics fields supported by the server.
-  // These values are externally declared in per-datatype .proto files.
-  optional int32 data_type_id = 1;
-
-  // An opaque-to-the-client sequence of bytes that the server may interpret
-  // as an indicator of the client's knowledge state.  If this is empty or
-  // omitted by the client, it indicates that the client is initiating a
-  // a first-time sync of this datatype.  Otherwise, clients must supply a
-  // value previously returned by the server in an earlier GetUpdatesResponse.
-  // These values are not comparable or generable on the client.
-  //
-  // The opaque semantics of this field are to afford server implementations
-  // some flexibility in implementing progress tracking.  For instance,
-  // a server implementation built on top of a distributed storage service --
-  // or multiple heterogenous such services -- might need to supply a vector
-  // of totally ordered monotonic update timestamps, rather than a single
-  // monotonically increasing value.  Other optimizations may also be
-  // possible if the server is allowed to embed arbitrary information in
-  // the progress token.
-  //
-  // Server implementations should keep the size of these tokens relatively
-  // small, on the order of tens of bytes, and they should remain small
-  // regardless of the number of items synchronized.  (A possible bad server
-  // implementation would be for progress_token to contain a list of all the
-  // items ever sent to the client.  Servers shouldn't do this.)
-  optional bytes token = 2;
-
-  // Clients that previously downloaded updates synced using the timestamp based
-  // progress tracking mechanism, but which wish to switch over to the opaque
-  // token mechanism can set this field in a GetUpdatesMessage.  The server
-  // will perform a get updates operation as normal from the indicated
-  // timestamp, and return only an opaque progress token.
-  optional int64 timestamp_token_for_migration = 3;
-
-  // An opaque-to-the-client string of bytes, received through a notification,
-  // that the server may interpret as a hint about the location of the latest
-  // version of the data for this type.
-  //
-  // Deprecated in M29.  We should use the repeated field version in the
-  // PerClientTypeState instead.
-  optional string notification_hint = 4;
-
-  // This field will be included only in GetUpdates with origin GU_TRIGGER.
-  optional GetUpdateTriggers get_update_triggers = 5;
-
-  // The garbage collection directive for this data type.  The client should
-  // purge items locally based on this directive.  Since this directive is
-  // designed to be sent from server only, the client should persist it locally
-  // as needed and avoid sending it to the server.
-  optional GarbageCollectionDirective gc_directive = 6;
-}
-
-message GetUpdatesMessage {
-  // Indicates the client's current progress in downloading updates.  A
-  // from_timestamp value of zero means that the client is requesting a first-
-  // time sync.  After that point, clients should fill in this value with the
-  // value returned in the last-seen GetUpdatesResponse.new_timestamp.
-  //
-  // from_timestamp has been deprecated; clients should use
-  // |from_progress_marker| instead, which allows more flexibility.
-  optional int64 from_timestamp = 1;
-
-  // Indicates the reason for the GetUpdatesMessage.
-  // Deprecated in M29.  We should eventually rely on GetUpdatesOrigin instead.
-  // Newer clients will support both systems during the transition period.
-  optional GetUpdatesCallerInfo caller_info = 2;
-
-  // Indicates whether related folders should be fetched.
-  optional bool fetch_folders = 3 [default = true];
-
-  // The presence of an individual EntitySpecifics field indicates that the
-  // client requests sync object types associated with that field.  This
-  // determination depends only on the presence of the field, not its
-  // contents -- thus clients should send empty messages as the field value.
-  // For backwards compatibility only bookmark objects will be sent to the
-  // client should requested_types not be present.
-  //
-  // requested_types may contain multiple EntitySpecifics fields -- in this
-  // event, the server will return items of all the indicated types.
-  //
-  // requested_types has been deprecated; clients should use
-  // |from_progress_marker| instead, which allows more flexibility.
-  optional EntitySpecifics requested_types = 4;
-
-  // Client-requested limit on the maximum number of updates to return at once.
-  // The server may opt to return fewer updates than this amount, but it should
-  // not return more.
-  optional int32 batch_size = 5;
-
-  // Per-datatype progress marker.  If present, the server will ignore
-  // the values of requested_types and from_timestamp, using this instead.
-  //
-  // With the exception of certain configuration or initial sync requests, the
-  // client should include one instance of this field for each enabled data
-  // type.
-  repeated DataTypeProgressMarker from_progress_marker = 6;
-
-  // Indicates whether the response should be sent in chunks.  This may be
-  // needed for devices with limited memory resources.  If true, the response
-  // will include one or more ClientToServerResponses, with the frist one
-  // containing GetUpdatesMetadataResponse, and the remaining ones, if any,
-  // containing GetUpdatesStreamingResponse.  These ClientToServerResponses are
-  // delimited by a length prefix, which is encoded as a varint.
-  optional bool streaming = 7 [default = false];
-
-  // Whether the client needs the server to provide an encryption key for this
-  // account.
-  // Note: this should typically only be set on the first GetUpdates a client
-  // requests. Clients are expected to persist the encryption key from then on.
-  // The allowed frequency for requesting encryption keys is much lower than
-  // other datatypes, so repeated usage will likely result in throttling.
-  optional bool need_encryption_key = 8 [default = false];
-
-  // Whether to create the mobile bookmarks folder if it's not
-  // already created.  Should be set to true only by mobile clients.
-  optional bool create_mobile_bookmarks_folder = 1000 [default = false];
-
-  // This value is an updated version of the GetUpdatesCallerInfo's
-  // GetUpdatesSource.  It describes the reason for the GetUpdate request.
-  // Introduced in M29.
-  optional SyncEnums.GetUpdatesOrigin get_updates_origin = 9;
-
-  // Whether this GU also serves as a retry GU. Any GU that happens after
-  // retry timer timeout is a retry GU effectively.
-  optional bool is_retry = 10 [default = false];
-
-  // Set of optional per-client datatype contexts.
-  repeated DataTypeContext client_contexts = 11;
-};
-
-message AuthenticateMessage {
-  required string auth_token = 1;
-};
-
-// Message from a client asking the server to clear its data.
-//
-// A client makes a ClearServerData request when it transitions to passphrase
-// encryption to ensure the server deletes any plaintext data that may have been
-// synced previously.
-message ClearServerDataMessage {
-  // No arguments needed as the store birthday and user identifier are part of
-  // an enclosing message.
-};
-
-// Response to a ClearServerData request.
-message ClearServerDataResponse {
-  // No result fields necessary. Success/failure is indicated in
-  // ClientToServerResponse.
-};
-
-message DeprecatedMessage1 {
-};
-
-message DeprecatedMessage2 {
-};
-
-// The client must preserve, store, and resend the chip bag with
-// every request.  The server depends on the chip bag in order
-// to precisely choreograph a client-server state machines.
-//
-// Because the client stores and sends this data on every request,
-// the contents of the chip bag should be kept relatively small.
-//
-// If the server does not return a chip bag, the client must assume
-// that there has been no change to the chip bag.  The client must
-// resend the bag of chips it had prior on the next request.
-//
-// The client must make the chip bag durable if and only if it
-// processes the response from the server.
-message ChipBag {
-  // Server chips are deliberately oqaque, allowing the server
-  // to encapsulate its state machine logic.
-  optional bytes server_chips = 1;
-}
-
-// Information about the syncer's state.
-message ClientStatus {
-  // Flag to indicate if the client has detected hierarchy conflcits.  The flag
-  // is left unset if update application has not been attempted yet.
-  //
-  // The server should attempt to resolve any hierarchy conflicts when this flag
-  // is set.  The client may not assume that any particular action will be
-  // taken.  There is no guarantee the problem will be addressed in a reasonable
-  // amount of time.
-  optional bool hierarchy_conflict_detected = 1;
-}
-
-// A single datatype's sync context. Allows the datatype to pass along
-// datatype specific information with its own server backend.
-message DataTypeContext {
-  // The type this context is associated with.
-  optional int32 data_type_id = 1;
-  // The context for the datatype.
-  optional bytes context = 2;
-  // The version of the context.
-  optional int64 version = 3;
-}
-
-message ClientToServerMessage {
-  // |share| field is only used on the server for logging and can sometimes
-  // contain empty string. It is still useful for logging username when it can't
-  // be derived from access token in case of auth error.
-  required string share = 1;
-
-  optional int32 protocol_version = 2 [default = 52];
-  enum Contents {
-    COMMIT = 1;
-    GET_UPDATES = 2;
-    AUTHENTICATE = 3;
-    DEPRECATED_4 = 4;
-    CLEAR_SERVER_DATA = 5;
-  }
-
-  // Each ClientToServerMessage contains one request defined by the
-  // message_contents. Each type has a corresponding message field that will be
-  // present iff the message is of that type. E.g. a commit message will have a
-  // message_contents of COMMIT and its commit field will be present.
-  required Contents message_contents = 3;
-  optional CommitMessage commit = 4;
-  optional GetUpdatesMessage get_updates = 5;
-  optional AuthenticateMessage authenticate = 6;
-
-  optional DeprecatedMessage1 deprecated_field_9 = 9 [deprecated = true];
-
-  optional string store_birthday = 7; // Opaque store ID; if it changes, duck!
-  // The client sets this if it detects a sync issue. The server will tell it
-  // if it should perform a refresh.
-  optional bool sync_problem_detected = 8 [default = false];
-
-  // Client side state information for debugging purpose.
-  // This is only sent on the first getupdates of every sync cycle,
-  // as an optimization to save bandwidth.
-  optional DebugInfo debug_info = 10;
-
-  // Per-client state for use by the server. Sent with every message sent to the
-  // server.
-  optional ChipBag bag_of_chips = 11;
-
-  // Google API key.
-  optional string api_key = 12;
-
-  // Client's self-reported state.
-  // The client should set this on every message sent to the server, though its
-  // member fields may often be unset.
-  optional ClientStatus client_status = 13;
-
-  // The ID that our invalidation client used to identify itself to the server.
-  // Sending the ID here allows the server to not send notifications of our own
-  // changes to our invalidator.
-  optional string invalidator_client_id = 14;
-
-  // Identifies this ClientToServerMessage as a clear server data request. This
-  // field is present when message_contents is CLEAR_SERVER_DATA.
-  optional ClearServerDataMessage clear_server_data = 15;
-};
-
-// This request allows the client to convert a specific crash identifier
-// into more general information (e.g. hash of the crashing call stack)
-// suitable for upload in an (authenticated) DebugInfo event.
-message GetCrashInfoRequest {
-  // Id of the uploaded crash.
-  optional string crash_id = 1;
-
-  // Time that the crash occurred.
-  optional int64 crash_time_millis = 2;
-}
-
-// Proto to be written in its entirety to the debug info log.
-message GetCrashInfoResponse {
-  // Hash of the crashing call stack.
-  optional string stack_id = 1;
-
-  // Time of the crash, potentially rounded to remove
-  // significant bits.
-  optional int64 crash_time_millis = 2;
-}
-
-message CommitResponse {
-  enum ResponseType {
-    SUCCESS = 1;
-    CONFLICT = 2; // You're out of date; update and check your data
-    // TODO(ncarter): What's the difference between RETRY and TRANSIENT_ERROR?
-    RETRY = 3; // Someone has a conflicting, non-expired session open
-    INVALID_MESSAGE = 4; // What the client sent was invalid, and trying again
-                         // won't help.
-    OVER_QUOTA = 5; // This operation would put you, or you are, over quota
-    TRANSIENT_ERROR = 6; // Something went wrong; try again in a bit
-  }
-  repeated group EntryResponse = 1 {
-    required ResponseType response_type = 2;
-
-    // Sync servers may also return a new ID for an existing item, indicating
-    // a new entry's been created to hold the data the client's sending up.
-    optional string id_string = 3;
-
-    // should be filled if our parent was assigned a new ID.
-    optional string parent_id_string = 4;
-
-    // This value is the same as the position_in_parent value returned within
-    // the SyncEntity message in GetUpdatesResponse.  There was a time when the
-    // client would attempt to honor this position, but nowadays the server
-    // should ensure it is no different from the position_in_parent sent up in
-    // the commit request and the client should not read it.
-    optional int64 position_in_parent = 5;
-
-    // The item's current version.
-    optional int64 version = 6;
-
-    // Allows the server to move-aside an entry as it's being committed.
-    // This name is the same as the name field returned within the SyncEntity
-    // message in GetUpdatesResponse.
-    optional string name = 7;
-
-    // This name is the same as the non_unique_name field returned within the
-    // SyncEntity message in GetUpdatesResponse.
-    optional string non_unique_name = 8;
-
-    optional string error_message = 9;
-
-    // Last modification time (in java time milliseconds).  Allows the server
-    // to override the client-supplied mtime during a commit operation.
-    optional int64 mtime = 10;
-  }
-};
-
-message GetUpdatesResponse {
-  // New sync entries that the client should apply.
-  repeated SyncEntity entries = 1;
-
-  // If there are more changes on the server that weren't processed during this
-  // GetUpdates request, the client should send another GetUpdates request and
-  // use new_timestamp as the from_timestamp value within GetUpdatesMessage.
-  //
-  // This field has been deprecated and will be returned only to clients
-  // that set the also-deprecated |from_timestamp| field in the update request.
-  // Clients should use |from_progress_marker| and |new_progress_marker|
-  // instead.
-  optional int64 new_timestamp = 2;
-
-  // DEPRECATED FIELD - server does not set this anymore.
-  optional int64 deprecated_newest_timestamp = 3;
-
-  // Approximate count of changes remaining - use this for UI feedback.
-  // If present and zero, this estimate is firm: the server has no changes
-  // after the current batch.
-  optional int64 changes_remaining = 4;
-
-  // Opaque, per-datatype timestamp-like tokens.  A client should use this
-  // field in lieu of new_timestamp, which is deprecated in newer versions
-  // of the protocol.  Clients should retain and persist the values returned
-  // in this field, and present them back to the server to indicate the
-  // starting point for future update requests.
-  //
-  // This will be sent only if the client provided |from_progress_marker|
-  // in the update request.
-  //
-  // The server may provide a new progress marker even if this is the end of
-  // the batch, or if there were no new updates on the server; and the client
-  // must save these.  If the server does not provide a |new_progress_marker|
-  // value for a particular datatype, when the request provided a
-  // |from_progress_marker| value for that datatype, the client should
-  // interpret this to mean "no change from the previous state" and retain its
-  // previous progress-marker value for that datatype.
-  //
-  // Progress markers in the context of a response will never have the
-  // |timestamp_token_for_migration| field set.
-  repeated DataTypeProgressMarker new_progress_marker = 5;
-
-  // The current encryption keys associated with this account. Will be set if
-  // the GetUpdatesMessage in the request had need_encryption_key == true or
-  // the server has updated the set of encryption keys (e.g. due to a key
-  // rotation).
-  repeated bytes encryption_keys = 6;
-
-  // Set of optional datatype contexts server mutations.
-  repeated DataTypeContext context_mutations = 7;
-};
-
-// The metadata response for GetUpdatesMessage.  This response is sent when
-// streaming is set to true in the request.  It is prefixed with a length
-// delimiter, which is encoded in varint.
-message GetUpdatesMetadataResponse {
-  // Approximate count of changes remaining.  Detailed comment is available in
-  // GetUpdatesResponse.
-  optional int64 changes_remaining = 1;
-
-  // Opaque, per-datatype timestamp-like tokens.  Detailed comment is available
-  // in GetUpdatesResponse.
-  repeated DataTypeProgressMarker new_progress_marker = 2;
-};
-
-// The streaming response message for GetUpdatesMessage.  This message is sent
-// when streaming is set to true in the request.  There may be multiple
-// GetUpdatesStreamingResponse messages in a response.  This type of messages
-// is preceded by GetUpdatesMetadataResponse.  It is prefixed with a length
-// delimiter, which is encoded in varint.
-message GetUpdatesStreamingResponse {
-  // New sync entries that the client should apply.
-  repeated SyncEntity entries = 1;
-};
-
-// A user-identifying struct.  For a given Google account the email and display
-// name can change, but obfuscated_id should be constant.
-// The obfuscated id is optional because at least one planned use of the proto
-// (sharing) does not require it.
-message UserIdentification {
-  required string email = 1;  // the user's full primary email address.
-  optional string display_name = 2;  // the user's display name.
-  optional string obfuscated_id = 3;  // an obfuscated, opaque user id.
-};
-
-message AuthenticateResponse {
-  // Optional only for backward compatibility.
-  optional UserIdentification user = 1;
-};
-
-message ThrottleParameters {
-  // Deprecated. Remove this from the server side.
-  required int32 min_measure_payload_size = 1;
-  required double target_utilization = 2;
-  required double measure_interval_max = 3;
-  required double measure_interval_min = 4;
-  required double observation_window = 5;
-};
-
-message ClientToServerResponse {
-  optional CommitResponse commit = 1;
-  optional GetUpdatesResponse get_updates = 2;
-  optional AuthenticateResponse authenticate = 3;
-
-  // Up until protocol_version 24, the default was SUCCESS which made it
-  // impossible to add new enum values since older clients would parse any
-  // out-of-range value as SUCCESS. Starting with 25, unless explicitly set,
-  // the error_code will be UNKNOWN so that clients know when they're
-  // out-of-date. Note also that when using protocol_version < 25,
-  // TRANSIENT_ERROR is not supported. Instead, the server sends back a HTTP
-  // 400 error code. This is deprecated now.
-  optional SyncEnums.ErrorType error_code = 4 [default = UNKNOWN];
-  optional string error_message = 5;
-
-  // Opaque store ID; if it changes, the contents of the client's cache
-  // is meaningless to this server.  This happens most typically when
-  // you switch from one storage backend instance (say, a test instance)
-  // to another (say, the official instance).
-  optional string store_birthday = 6;
-
-  optional ClientCommand client_command = 7;
-  optional ProfilingData profiling_data = 8;
-  optional DeprecatedMessage2 deprecated_field_9 = 9 [deprecated = true];
-  optional GetUpdatesMetadataResponse stream_metadata = 10;
-  // If GetUpdatesStreamingResponse is contained in the ClientToServerResponse,
-  // none of the other fields (error_code and etc) will be set.
-  optional GetUpdatesStreamingResponse stream_data = 11;
-
-  // The data types whose storage has been migrated.  Present when the value of
-  // error_code is MIGRATION_DONE.
-  repeated int32 migrated_data_type_id = 12;
-
-  message Error {
-    optional SyncEnums.ErrorType error_type = 1 [default = UNKNOWN];
-    optional string error_description       = 2;
-    optional string url                     = 3;
-    optional SyncEnums.Action action        = 4 [default = UNKNOWN_ACTION];
-
-    // Currently meaningful if |error_type| is throttled or partial_failure.
-    // In the throttled case, if this field is absent then the whole client
-    // (all datatypes) is throttled.
-    // In the partial_failure case, this field denotes partial failures. The
-    // client should retry those datatypes with exponential backoff.
-    repeated int32 error_data_type_ids = 5;
-  }
-  optional Error error = 13;
-
-  // The new per-client state for this client. If set, should be persisted and
-  // sent with any subsequent ClientToServerMessages.
-  optional ChipBag new_bag_of_chips = 14;
-
-  // Present if this ClientToServerResponse is in response to a ClearServerData
-  // request.
-  optional ClearServerDataResponse clear_server_data = 15;
-};
-
-// A message to notify the server of certain sync events. Idempotent. Send these
-// to the /event endpoint.
-message EventRequest {
-  optional SyncDisabledEvent sync_disabled = 1;
-};
-
-message EventResponse {
-};
-
-// A message indicating that the sync engine has been disabled on a client.
-message SyncDisabledEvent {
-  // The GUID that identifies the sync client.
-  optional string cache_guid = 1;
-
-  // The store birthday that the client was using before disabling sync.
-  optional string store_birthday = 2;
-};