sync: Expose sync functionality as functions

sync/engine/syncer.h

Index: sync/engine/syncer.h
diff --git a/sync/engine/syncer.h b/sync/engine/syncer.h
index 8656e7c2cabf6af93f79601c2725008195558a98..82bbca07acee86967ca734dfad9d5840e3824cd2 100644
--- a/sync/engine/syncer.h
+++ b/sync/engine/syncer.h
@@ -20,21 +20,6 @@
 
 namespace syncer {
 
-namespace syncable {
-class Entry;
-class MutableEntry;
-}  // namespace syncable
-
-enum SyncerStep {
-  SYNCER_BEGIN,
-  DOWNLOAD_UPDATES,
-  PROCESS_UPDATES,
-  STORE_TIMESTAMPS,
-  APPLY_UPDATES,
-  COMMIT,
-  SYNCER_END
-};
-
 // A Syncer provides a control interface for driving the individual steps
 // of the sync cycle.  Each cycle (hopefully) moves the client into closer
 // synchronization with the server.  The individual steps are modeled
@@ -57,14 +42,17 @@ class SYNC_EXPORT_PRIVATE Syncer {
   bool ExitRequested();
   void RequestEarlyExit();
 
-  // Runs a sync cycle from |first_step| to |last_step|.
-  // Returns true if the cycle completed with |last_step|, and false
-  // if it terminated early due to error / exit requested.
-  virtual bool SyncShare(sessions::SyncSession* session,
-                         SyncerStep first_step,
-                         SyncerStep last_step);
+  virtual bool NormalSyncShare(sessions::SyncSession* session,
+                               ModelTypeSet request_types,
+                               const sessions::NudgeTracker& nudge_tracker);
+  virtual bool ConfigureSyncShare(sessions::SyncSession* session,
+                                  ModelTypeSet request_types);
+  virtual bool PollSyncShare(sessions::SyncSession* session,
+                             ModelTypeSet request_types);
 
  private:
+  void ApplyUpdates(sessions::SyncSession* session);
+
   bool early_exit_requested_;
   base::Lock early_exit_requested_lock_;
 
@@ -93,10 +81,6 @@ class SYNC_EXPORT_PRIVATE Syncer {
   DISALLOW_COPY_AND_ASSIGN(Syncer);
 };
 
-// Utility function declarations.
-void CopyServerFields(syncable::Entry* src, syncable::MutableEntry* dest);
-const char* SyncerStepToString(const SyncerStep);
-
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_SYNCER_H_