Support browser side thumbnailing for GPU composited pages on Windows.

content/public/browser/render_widget_host_view.h

Index: content/public/browser/render_widget_host_view.h
diff --git a/content/public/browser/render_widget_host_view.h b/content/public/browser/render_widget_host_view.h
index db457db7745aa9c733a182dcbeae29a07063e348..18ceb1c525df763c29aa4900506e5194b4870e51 100644
--- a/content/public/browser/render_widget_host_view.h
+++ b/content/public/browser/render_widget_host_view.h
@@ -23,6 +23,10 @@ class Rect;
 class Size;
 }
 
+namespace skia {
+class PlatformCanvas;
+}
+
 namespace content {
 
 class RenderWidgetHost;
@@ -134,6 +138,12 @@ class CONTENT_EXPORT RenderWidgetHostView {
   virtual void SetBackground(const SkBitmap& background) = 0;
   virtual const SkBitmap& GetBackground() = 0;
 
+  // Copies the contents of the compositing surface into the given
+  // (uninitialized) PlatformCanvas if any. Returns true on success, false
+  // otherwise.
+  virtual bool CopyFromCompositingSurface(const gfx::Size& size,
+                                          skia::PlatformCanvas* output) = 0;
+
   // TODO(joi): Remove this when we remove the dependency by chrome/
   // on browser_accessibility* files in content.
   virtual BrowserAccessibilityManager*