Improvements to uses of base::SmallMap

cc/scheduler/begin_frame_source.h

Index: cc/scheduler/begin_frame_source.h
diff --git a/cc/scheduler/begin_frame_source.h b/cc/scheduler/begin_frame_source.h
index 5831339961733c726cc9fef4e23c75e9fc216a57..48a40dcf8b17b1b326939c1d7b6e2741967c0288 100644
--- a/cc/scheduler/begin_frame_source.h
+++ b/cc/scheduler/begin_frame_source.h
@@ -283,7 +283,7 @@ class CC_EXPORT BeginFrameObserverAckTracker {
   base::flat_set<BeginFrameObserver*> observers_;
   base::flat_set<BeginFrameObserver*> finished_observers_;
   bool observers_had_damage_ = false;
-  base::SmallMap<std::map<BeginFrameObserver*, uint64_t>, 4>
+  base::small_map<std::map<BeginFrameObserver*, uint64_t>, 4>

[danakj, 2017/04/18 21:35:50]

This should really be a flat_map, there's no way this is getting so large that a
map is a good idea, and it rarely changes.

       latest_confirmed_sequence_numbers_;
 
   DISALLOW_COPY_AND_ASSIGN(BeginFrameObserverAckTracker);