Support browser side thumbnailing for GPU composited pages on Windows.

content/browser/renderer_host/render_widget_host_view_win.cc

Index: content/browser/renderer_host/render_widget_host_view_win.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_win.cc b/content/browser/renderer_host/render_widget_host_view_win.cc
index 9f598b713d8a7d0f67a5ca4ff62b0467a244a20a..7346c78e3609e584109ae33cf2dccd4e87466b8f 100644
--- a/content/browser/renderer_host/render_widget_host_view_win.cc
+++ b/content/browser/renderer_host/render_widget_host_view_win.cc
@@ -908,6 +908,22 @@ void RenderWidgetHostViewWin::SetBackground(const SkBitmap& background) {
   render_widget_host_->SetBackground(background);
 }
 
+bool RenderWidgetHostViewWin::CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) {
+  if (!accelerated_surface_.get())
+    return false;
+
+  if (size.IsEmpty())
+    return false;
+
+  if (!output->initialize(size.width(), size.height(), true))
+    return false;
+
+  return accelerated_surface_->CopyTo(
+      size, output->getTopDevice()->accessBitmap(true).getPixels());
+}
+
 void RenderWidgetHostViewWin::UnhandledWheelEvent(
     const WebKit::WebMouseWheelEvent& event) {
 }