Use inner HWND for accelerated rendering on windows

chrome/gpu/gpu_channel.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/gpu/gpu_channel.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
@@ skipping 105 matching lines @@
   gfx::PluginWindowHandle handle = gfx::kNullPluginWindow;
 #if defined(OS_WIN)
   gfx::NativeView view = gfx::NativeViewFromId(view_id);
 
   // Check that the calling renderer is allowed to render to this window.
   // TODO(apatrick): consider killing the renderer process rather than failing.
   int view_renderer_id = reinterpret_cast<int>(
       GetProp(view, chrome::kChromiumRendererIdProperty));
   if (view_renderer_id != renderer_id_)
     return;
+
+  // Note, we don't actually render into the view HWND. Instead, inside
+  // the GpuCommandBufferStub, we will create a child window within the view
+  // HWND into which we will render.
   handle = view;
 #elif defined(OS_LINUX)
   ChildThread* gpu_thread = ChildThread::current();
   // Ask the browser for the view's XID.
   // TODO(piman): This assumes that it doesn't change. It can change however
   // when tearing off tabs. This needs a fix in the browser UI code. A possible
   // alternative would be to add a socket/plug pair like with plugins but that
   // has issues with events and focus.
   gpu_thread->Send(new GpuHostMsg_GetViewXID(view_id, &handle));
 #elif defined(OS_MACOSX)
@@ skipping 108 matching lines @@
       channel_name, IPC::Channel::MODE_SERVER, this, NULL,
       ChildProcess::current()->io_message_loop(), false,
       ChildProcess::current()->GetShutDownEvent()));
 
   return true;
 }
 
 std::string GpuChannel::GetChannelName() {
   return StringPrintf("%d.r%d", base::GetCurrentProcId(), renderer_id_);
 }