Mac Overlays: Add sandwich strategy

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:
+  // State from the renderer that is relevant to the overlay processor
+  // strategies.
+  struct CC_EXPORT RendererState {
+    RendererState();
+    ~RendererState();
+    float device_scale_factor;
+  };
   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_in_draw_order|.
-    virtual bool Attempt(RenderPassList* render_passes_in_draw_order,
+    virtual bool Attempt(const RendererState& renderer_state,
+                         RenderPassList* render_passes_in_draw_order,
                          OverlayCandidateList* candidates) = 0;
   };
   typedef ScopedPtrVector<Strategy> StrategyList;
 
   explicit OverlayProcessor(OutputSurface* surface);
   virtual ~OverlayProcessor();
   // Virtual to allow testing different strategies.
   virtual void Initialize();
 
-  void ProcessForOverlays(RenderPassList* render_passes_in_draw_order,
+  void ProcessForOverlays(const RendererState& renderer_state,
+                          RenderPassList* render_passes_in_draw_order,
                           OverlayCandidateList* candidate_list);
 
  protected:
   StrategyList strategies_;
   OutputSurface* surface_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OverlayProcessor);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OVERLAY_PROCESSOR_H_