Support browser side thumbnailing for GPU composited pages on Windows.

content/browser/renderer_host/render_widget_host_view_gtk.cc

Index: content/browser/renderer_host/render_widget_host_view_gtk.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_gtk.cc b/content/browser/renderer_host/render_widget_host_view_gtk.cc
index a2cf64ee66b8c182fe37a9221c95b5ca9546c3cc..fa4b8792989074456d8fc6c155c0ef7c48574a9d 100644
--- a/content/browser/renderer_host/render_widget_host_view_gtk.cc
+++ b/content/browser/renderer_host/render_widget_host_view_gtk.cc
@@ -1047,6 +1047,14 @@ void RenderWidgetHostViewGtk::SetBackground(const SkBitmap& background) {
   host_->Send(new ViewMsg_SetBackground(host_->GetRoutingID(), background));
 }
 
+bool RenderWidgetHostViewGtk::CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) {
+  // TODO(mazda): Implement this.
+  NOTIMPLEMENTED();
+  return false;
+}
+
 void RenderWidgetHostViewGtk::ModifyEventForEdgeDragging(
     GtkWidget* widget, GdkEventMotion* event) {
   // If the widget is aligned with an edge of the monitor its on and the user