sync: make scheduling logic and job ownership more obvious.

sync/engine/syncer.h

 // 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.
 
 #ifndef SYNC_ENGINE_SYNCER_H_
 #define SYNC_ENGINE_SYNCER_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 41 matching lines @@
 
   Syncer();
   virtual ~Syncer();
 
   // Called by other threads to tell the syncer to stop what it's doing
   // and return early from SyncShare, if possible.
   bool ExitRequested();
   void RequestEarlyExit();
 
   // Runs a sync cycle from |first_step| to |last_step|.
-  virtual void SyncShare(sessions::SyncSession* session,
+  // 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);
 
  private:
   bool early_exit_requested_;
   base::Lock early_exit_requested_lock_;
 
   ConflictResolver resolver_;
 
   friend class SyncerTest;
@@ skipping 22 matching lines @@
 };
 
 // Utility function declarations.
 void CopyServerFields(syncable::Entry* src, syncable::MutableEntry* dest);
 void ClearServerData(syncable::MutableEntry* entry);
 const char* SyncerStepToString(const SyncerStep);
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_SYNCER_H_