sync: Expose sync functionality as functions

sync/sessions/nudge_tracker.h

Index: sync/sessions/nudge_tracker.h
diff --git a/sync/sessions/nudge_tracker.h b/sync/sessions/nudge_tracker.h
index 3db3143d4752d13dbe4f9dc3f607e31e7c0ac898..0e8ab51202c058b8f72d115e5f21d5eba7c174de 100644
--- a/sync/sessions/nudge_tracker.h
+++ b/sync/sessions/nudge_tracker.h
@@ -32,7 +32,7 @@ class SYNC_EXPORT_PRIVATE NudgeTracker {
   // Returns true if there is a good reason for performing a sync cycle.
   // This does not take into account whether or not this is a good *time* to
   // perform a sync cycle; that's the scheduler's job.
-  bool IsSyncRequired();
+  bool IsSyncRequired() const;
 
   // Tells this class that all required update fetching and committing has
   // completed successfully.
@@ -88,13 +88,20 @@ class SYNC_EXPORT_PRIVATE NudgeTracker {
   // See the implementation for important information about the coalesce logic.
   sync_pb::GetUpdatesCallerInfo::GetUpdatesSource updates_source() const;
 
-  // Fills a ProgressMarker for the next GetUpdates request.  This is used by
-  // the DownloadUpdatesCommand to dump lots of useful per-type state
+  // Fills a GetUpdatesTrigger message for the next GetUpdates request.  This is
+  // used by the DownloadUpdatesCommand to dump lots of useful per-type state
   // information into the GetUpdate request before sending it off to the server.
   void FillProtoMessage(
       ModelType type,
       sync_pb::GetUpdateTriggers* msg) const;
 
+  // Fills a ProgressMarker with single legacy notification hint expected by the
+  // sync server.  Newer servers will rely on the data set by FillProtoMessage()
+  // instead of this.
+  void SetLegacyNotificationHint(
+      ModelType type,
+      sync_pb::DataTypeProgressMarker* progress) const;
+
   // Adjusts the number of hints that can be stored locally.
   void SetHintBufferSize(size_t size);