List all child surfaces (including occluded) in CompositorFrame

cc/output/compositor_frame_metadata.h

 // Copyright (c) 2012 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_OUTPUT_COMPOSITOR_FRAME_METADATA_H_
 #define CC_OUTPUT_COMPOSITOR_FRAME_METADATA_H_
 
 #include <vector>
 
 #include "cc/base/cc_export.h"
 #include "cc/output/viewport_selection_bound.h"
+#include "cc/surfaces/surface_id.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/events/latency_info.h"
 #include "ui/gfx/geometry/size_f.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 
 namespace cc {
 
 class CC_EXPORT CompositorFrameMetadata {
  public:
   CompositorFrameMetadata();
@@ skipping 28 matching lines @@
 
   // Provides selection region updates relative to the current viewport. If the
   // selection is empty or otherwise unused, the bound types will indicate such.
   ViewportSelection selection;
 
   std::vector<ui::LatencyInfo> latency_info;
 
   // A set of SurfaceSequences that this frame satisfies (always in the same
   // namespace as the current Surface).
   std::vector<uint32_t> satisfies_sequences;
+
+  // This is the set of Surfaces that are referenced by this frame.
+  std::vector<SurfaceId> referenced_surfaces;
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_COMPOSITOR_FRAME_METADATA_H_