Allow layers to signal that additional sequences are needed before surface destruction

cc/surfaces/surface.h

 // Copyright 2014 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_H_
 #define CC_SURFACES_SURFACE_H_
 
 #include <map>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/quads/render_pass_id.h"
 #include "cc/surfaces/surface_id.h"
+#include "cc/surfaces/surface_sequence.h"
 #include "cc/surfaces/surfaces_export.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace ui {
 struct LatencyInfo;
 }
 
 namespace cc {
 class CompositorFrame;
 class CopyOutputRequest;
@@ skipping 19 matching lines @@
   // Returns the most recent frame that is eligible to be rendered.
   const CompositorFrame* GetEligibleFrame();
 
   // Returns a number that increments by 1 every time a new frame is enqueued.
   int frame_index() const { return frame_index_; }
 
   void TakeLatencyInfo(std::vector<ui::LatencyInfo>* latency_info);
   void RunDrawCallbacks();
 
   base::WeakPtr<SurfaceFactory> factory() { return factory_; }
+  base::hash_set<SurfaceSequence>& destruction_dependencies() {
+    return destruction_dependencies_;
+  }
 
  private:
   void ClearCopyRequests();
 
   SurfaceId surface_id_;
   gfx::Size size_;
   base::WeakPtr<SurfaceFactory> factory_;
   // TODO(jamesr): Support multiple frames in flight.
   scoped_ptr<CompositorFrame> current_frame_;
   int frame_index_;
+  base::hash_set<SurfaceSequence> destruction_dependencies_;

[piman, 2014/11/05 00:36:15]

Could this be a vector? AFAICT the only things that write into the set is the
RequireCallback that is only called with a new sequence, and the erase (so
you're guaranteed to have unique entries, you could DCHECK it even). It's only
read sequentially too.

 
   base::Closure draw_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Surface);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_H_