Surface synchronization: Immediately activate late arriving CompositorFrames

cc/surfaces/surface_dependency_tracker.h

 // Copyright 2017 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 CC_SURFACES_SURFACE_DEPENDENCY_TRACKER_H_
 #define CC_SURFACES_SURFACE_DEPENDENCY_TRACKER_H_
 
 #include "cc/scheduler/begin_frame_source.h"
 #include "cc/surfaces/pending_frame_observer.h"
 #include "cc/surfaces/surface.h"
@@ skipping 69 matching lines @@
   base::Optional<uint32_t> frames_since_deadline_set_;
 
   // A map from a SurfaceId to the set of Surfaces blocked on that SurfaceId.
   std::unordered_map<SurfaceId, base::flat_set<SurfaceId>, SurfaceIdHash>
       blocked_surfaces_from_dependency_;
 
   // The set of SurfaceIds corresponding to observed Surfaces that have
   // blockers.
   base::flat_set<SurfaceId> observed_surfaces_by_id_;
 
+  // The set of SurfaceIds to which corresponding CompositorFrames have not
+  // arrived by the time their deadline fired.
+  base::flat_set<SurfaceId> late_surfaces_by_id_;
+
   DISALLOW_COPY_AND_ASSIGN(SurfaceDependencyTracker);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_DEPENDENCY_TRACKER_H_