Support browser side thumbnailing for GPU composited pages on Windows.

content/browser/renderer_host/render_widget_host.h

Index: content/browser/renderer_host/render_widget_host.h
diff --git a/content/browser/renderer_host/render_widget_host.h b/content/browser/renderer_host/render_widget_host.h
index 7abb5479f4bfd8705a0108cd62e06bc4a1242dff..da4f2dd3e088567bbceac920879aeedd55a1143b 100644
--- a/content/browser/renderer_host/render_widget_host.h
+++ b/content/browser/renderer_host/render_widget_host.h
@@ -112,6 +112,11 @@ class CONTENT_EXPORT RenderWidgetHost {
   // PlatformCanvas. Returns true on success, false otherwise.
   virtual bool CopyFromBackingStore(skia::PlatformCanvas* output) = 0;
 
+  // Copies the contents of the compositing surface into the given
+  // (uninitialized) PlatformCanvas if any. Returns true on success, false
+  // otherwise.
+  virtual bool CopyFromCompositingSurface(skia::PlatformCanvas* output) = 0;
+
 #if defined(TOOLKIT_GTK)
   // Paint the backing store into the target's |dest_rect|.
   virtual bool CopyFromBackingStoreToGtkWindow(const gfx::Rect& dest_rect,
@@ -324,6 +329,8 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
   void SetIsLoading(bool is_loading);
 
   virtual bool CopyFromBackingStore(skia::PlatformCanvas* output) OVERRIDE;
+  virtual bool CopyFromCompositingSurface(
+      skia::PlatformCanvas* output) OVERRIDE;
 #if defined(TOOLKIT_GTK)
   virtual bool CopyFromBackingStoreToGtkWindow(const gfx::Rect& dest_rect,
                                                GdkWindow* target) OVERRIDE;