Drop frontbuffers with ui-use-gpu-process, synchronized with browser, decoupled from backbuffer dro…

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index f1ac5eb1d45479201ef92fb9a04b5337926e5ab0..684d7ebcae41764e11fe3b6b0055dc18e253983f 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -152,6 +152,7 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   // having been hidden.
   void WasHidden();
   void WasRestored();
+  bool IsVisible() const { return !is_hidden_; }
 
   // Called to notify the RenderWidget that its associated native window got
   // focused.
@@ -356,6 +357,16 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   static void AcknowledgeSwapBuffers(int32 route_id, int gpu_host_id);
   static void AcknowledgePostSubBuffer(int32 route_id, int gpu_host_id);
 
+#if defined(USE_AURA)
+  // Called by the view in response to visibility changes once the front surface
+  // is no longer in use by the ui (false), or when we expect to have a valid
+  // front surface for use by the ui (true).
+  static void SendFrontSurfaceIsProtected(bool is_protected,
+                                          uint32 protection_state_id,
+                                          int32 route_id,
+                                          int gpu_host_id);
+#endif
+
   // Signals that the compositing surface was updated, e.g. after a lost context
   // event.
   void CompositingSurfaceUpdated();