[Sync] Make BackendMigrator not wait for full sync cycles

chrome/browser/sync/engine/sync_scheduler.h

Index: chrome/browser/sync/engine/sync_scheduler.h
diff --git a/chrome/browser/sync/engine/sync_scheduler.h b/chrome/browser/sync/engine/sync_scheduler.h
index 1c0c9f999752411cb358c5bf4f7f63413101a203..2f0dd6a76c3bbf52d31b699e99d22e85be9ec1b1 100644
--- a/chrome/browser/sync/engine/sync_scheduler.h
+++ b/chrome/browser/sync/engine/sync_scheduler.h
@@ -97,6 +97,10 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
       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.
@@ -312,7 +316,6 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
       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;