[Sync] Make BackendMigrator not wait for full sync cycles

chrome/browser/sync/engine/sync_scheduler.h

 // Copyright (c) 2011 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.
 //
 // A class to schedule syncer tasks intelligently.
 #ifndef CHROME_BROWSER_SYNC_ENGINE_SYNC_SCHEDULER_H_
 #define CHROME_BROWSER_SYNC_ENGINE_SYNC_SCHEDULER_H_
 #pragma once
 
 #include <string>
@@ skipping 79 matching lines @@
       const syncable::ModelTypePayloadMap& types_with_payloads,
       const tracked_objects::Location& nudge_location);
 
   // Note: The source argument of this function must come from the subset of
   // GetUpdatesCallerInfo values related to configurations.
   void ScheduleConfig(
       const syncable::ModelTypeBitSet& types,
       sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
 
   void ScheduleClearUserData();
+  // If this is called before Start(), the cleanup is guaranteed to
+  // happen before the Start finishes.
+  //
+  // TODO(akalin): Figure out how to test this.
   void ScheduleCleanupDisabledTypes();
 
   // Change status of notifications in the SyncSessionContext.
   void set_notifications_enabled(bool notifications_enabled);
 
   base::TimeDelta sessions_commit_delay() const;
 
   // DDOS avoidance function.  Calculates how long we should wait before trying
   // again after a failed sync attempt, where the last delay was |base_delay|.
   // TODO(tim): Look at URLRequestThrottlerEntryInterface.
@@ skipping 195 matching lines @@
   void StartImpl(Mode mode, ModeChangeCallback* callback);
   void ScheduleNudgeImpl(
       const base::TimeDelta& delay,
       sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source,
       const syncable::ModelTypePayloadMap& types_with_payloads,
       bool is_canary_job, const tracked_objects::Location& nudge_location);
   void ScheduleConfigImpl(const ModelSafeRoutingInfo& routing_info,
       const std::vector<ModelSafeWorker*>& workers,
       const sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
   void ScheduleClearUserDataImpl();
-  void ScheduleCleanupDisabledTypesImpl();
 
   // Returns true if the client is currently in exponential backoff.
   bool IsBackingOff() const;
 
   // Helper to signal all listeners registered with |session_context_|.
   void Notify(SyncEngineEvent::EventCause cause);
 
   // Callback to change backoff state.
   void DoCanaryJob();
   void Unthrottle();
@@ skipping 76 matching lines @@
   scoped_ptr<Syncer> syncer_;
 
   scoped_ptr<sessions::SyncSessionContext> session_context_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncScheduler);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_ENGINE_SYNC_SCHEDULER_H_