Mac gpu: on gpu<->nongpu transitions, make sure to not show uninitialized memory

chrome/browser/renderer_host/accelerated_surface_container_manager_mac.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/renderer_host/accelerated_surface_container_manager_mac.h"
 
 #include "base/logging.h"
 #include "chrome/browser/renderer_host/accelerated_surface_container_mac.h"
 #include "webkit/glue/plugins/webplugin.h"
 
@@ skipping 35 matching lines @@
   }
   plugin_window_to_container_map_.erase(id);
 }
 
 bool AcceleratedSurfaceContainerManagerMac::IsRootContainer(
     gfx::PluginWindowHandle id) const {
   return root_container_handle_ != gfx::kNullPluginWindow &&
       root_container_handle_ == id;
 }
 
+void AcceleratedSurfaceContainerManagerMac::
+    set_gpu_rendering_active(bool active) {
+  if (gpu_rendering_active_ && !active)
+    SetRootSurfaceInvalid();
+  gpu_rendering_active_ = active;
+}
+
 void AcceleratedSurfaceContainerManagerMac::SetSizeAndIOSurface(
     gfx::PluginWindowHandle id,
     int32 width,
     int32 height,
     uint64 io_surface_identifier) {
   AutoLock lock(lock_);
 
   AcceleratedSurfaceContainerMac* container = MapIDToContainer(id);
   if (container) {
     container->SetSizeAndIOSurface(width, height, io_surface_identifier);
@@ skipping 59 matching lines @@
 
 void AcceleratedSurfaceContainerManagerMac::SetSurfaceWasPaintedTo(
     gfx::PluginWindowHandle id, uint64 surface_id) {
   AutoLock lock(lock_);
 
   AcceleratedSurfaceContainerMac* container = MapIDToContainer(id);
   if (container)
     container->set_was_painted_to(surface_id);
 }
 
+void AcceleratedSurfaceContainerManagerMac::SetRootSurfaceInvalid() {
+  AutoLock lock(lock_);
+  if (root_container_)
+    root_container_->set_surface_invalid();
+}
+
 bool AcceleratedSurfaceContainerManagerMac::SurfaceShouldBeVisible(
     gfx::PluginWindowHandle id) const {
   AutoLock lock(lock_);
 
   if (IsRootContainer(id) && !gpu_rendering_active_)
     return false;
 
   AcceleratedSurfaceContainerMac* container = MapIDToContainer(id);
   return container && container->should_be_visible();
 }
 
 AcceleratedSurfaceContainerMac*
     AcceleratedSurfaceContainerManagerMac::MapIDToContainer(
         gfx::PluginWindowHandle id) const {
   PluginWindowToContainerMap::const_iterator i =
       plugin_window_to_container_map_.find(id);
   if (i != plugin_window_to_container_map_.end())
     return i->second;
 
   LOG(ERROR) << "Request for plugin container for unknown window id " << id;
 
   return NULL;
 }