[Sync] Sync types never recovers from throttle

components/sync/engine_impl/sync_scheduler_impl.h

Index: components/sync/engine_impl/sync_scheduler_impl.h
diff --git a/components/sync/engine_impl/sync_scheduler_impl.h b/components/sync/engine_impl/sync_scheduler_impl.h
index edf0e1c1904ad484f9ae02124a08631a0f949bcc..67c1cd8cd1e9dae434748ea621571d630cc263d7 100644
--- a/components/sync/engine_impl/sync_scheduler_impl.h
+++ b/components/sync/engine_impl/sync_scheduler_impl.h
@@ -216,6 +216,8 @@ class SyncSchedulerImpl : public SyncScheduler, public base::NonThreadSafe {
   // is the most flexible place to do this bookkeeping.
   void UpdateNudgeTimeRecords(ModelTypeSet types);
 
+  bool IsEarlierThanCurrentPendingJob(const base::TimeDelta& delay);
+
   // Used for logging.
   const std::string name_;
 
@@ -240,6 +242,8 @@ class SyncSchedulerImpl : public SyncScheduler, public base::NonThreadSafe {
 
   std::unique_ptr<BackoffDelayProvider> delay_provider_;
 
+  // TODO(gangwu): http://crbug.com/714868 too many timers in this class, try to
+  // reduce them.
   // The event that will wake us up.
   // When the whole client got throttling or backoff, we will delay this timer
   // as well.