Avoid Copying damage rect when using Overlays

cc/output/overlay_processor.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_OUTPUT_OVERLAY_PROCESSOR_H_
 #define CC_OUTPUT_OVERLAY_PROCESSOR_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/output/overlay_candidate.h"
 #include "cc/quads/render_pass.h"
 
 namespace cc {
 class OutputSurface;
 class ResourceProvider;
 
 class CC_EXPORT OverlayProcessor {
  public:
   class CC_EXPORT Strategy {
    public:
     virtual ~Strategy() {}
     // Returns false if the strategy cannot be made to work with the
     // current set of render passes. Returns true if the strategy was successful
     // and adds any additional passes necessary to represent overlays to
-    // |render_passes|.
+    // |render_passes|. Strategy can also optimize |damage_rect| as it seems
+    // fit to reduce GL composition, in case |damage_rect| is obscured by
+    // overlays.
     virtual bool Attempt(ResourceProvider* resource_provider,
                          RenderPassList* render_passes,
-                         OverlayCandidateList* candidates) = 0;
+                         OverlayCandidateList* candidates,
+                         gfx::Rect* damage_rect) = 0;
   };
   typedef ScopedPtrVector<Strategy> StrategyList;
 
   explicit OverlayProcessor(OutputSurface* surface);
   virtual ~OverlayProcessor();
   // Virtual to allow testing different strategies.
   virtual void Initialize();
 
   void ProcessForOverlays(ResourceProvider* resource_provider,
                           RenderPassList* render_passes,
-                          OverlayCandidateList* candidates);
+                          OverlayCandidateList* candidates,
+                          gfx::Rect* damage_rect);
 
  protected:
   StrategyList strategies_;
   OutputSurface* surface_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OverlayProcessor);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OVERLAY_PROCESSOR_H_