cc: Don't do CompositeAndReadback when using DelegatingRenderer.

cc/output/delegating_renderer.h

Index: cc/output/delegating_renderer.h
diff --git a/cc/output/delegating_renderer.h b/cc/output/delegating_renderer.h
index 813be91504430e701eed3989b9f3d2cbb5ba26bf..6e659c06cab458546f4c1109b3480c6404090cfb 100644
--- a/cc/output/delegating_renderer.h
+++ b/cc/output/delegating_renderer.h
@@ -7,6 +7,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
+#include "cc/output/compositor_frame.h"
 #include "cc/output/renderer.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebGraphicsContext3D.h"
 
@@ -25,6 +26,8 @@ class CC_EXPORT DelegatingRenderer : public Renderer {
 
   virtual const RendererCapabilities& Capabilities() const OVERRIDE;
 
+  virtual bool CanReadPixels() const OVERRIDE;
+
   virtual void DrawFrame(RenderPassList* render_passes_in_draw_order) OVERRIDE;
 
   virtual void Finish() OVERRIDE {}
@@ -52,8 +55,8 @@ class CC_EXPORT DelegatingRenderer : public Renderer {
   OutputSurface* output_surface_;
   ResourceProvider* resource_provider_;
   RendererCapabilities capabilities_;
+  CompositorFrame frame_for_swap_buffers_;
   bool visible_;
-  RenderPassList render_passes_for_swap_buffers_;
 
   DISALLOW_COPY_AND_ASSIGN(DelegatingRenderer);
 };