Added command buffer implementation of WebGL which runs in the sandbox....

chrome/renderer/render_thread.h

Index: chrome/renderer/render_thread.h
===================================================================
--- chrome/renderer/render_thread.h	(revision 42776)
+++ chrome/renderer/render_thread.h	(working copy)
@@ -172,6 +172,12 @@
   // Use GetGpuChannel() to determine when the channel is ready for use.
   void EstablishGpuChannel();
 
+  // Synchronously establish a channel to the GPU plugin if not previously
+  // established or if it has been lost (for example if the GPU plugin crashed).
+  // If there is a pending asynchronous request, it will be completed by the
+  // time this routine returns.
+  GpuChannelHost* EstablishGpuChannelSync();
+
   // Get the GPU channel. Returns NULL if the channel is not established or
   // has been lost.
   GpuChannelHost* GetGpuChannel();