Command to mark surface inactive, so gpu process can release resources.

content/common/gpu/image_transport_surface.h

Index: content/common/gpu/image_transport_surface.h
diff --git a/content/common/gpu/image_transport_surface.h b/content/common/gpu/image_transport_surface.h
index 044d8c3231e0c67cf8c01ed8b24f5dbc4ca69a23..fc9e951b93285ff9a63980dbd7e399d2c32bc412 100644
--- a/content/common/gpu/image_transport_surface.h
+++ b/content/common/gpu/image_transport_surface.h
@@ -52,6 +52,7 @@ class ImageTransportSurface {
       uint64 surface_id, TransportDIB::Handle surface_handle) = 0;
   virtual void OnBuffersSwappedACK() = 0;
   virtual void OnResize(gfx::Size size) = 0;
+  virtual void OnSurfaceVisible(bool visible) = 0;
 
   // Creates the appropriate surface depending on the GL implementation.
   static scoped_refptr<gfx::GLSurface>
@@ -104,6 +105,7 @@ class ImageTransportHelper : public IPC::Channel::Listener {
 
   // Backbuffer resize callback.
   void Resize(gfx::Size size);
+  void SurfaceVisible(bool visible);
 
   // Weak pointers that point to objects that outlive this helper.
   ImageTransportSurface* surface_;