Added CommandBuffer::GetLastError.

content/renderer/gpu/command_buffer_proxy.cc

Index: content/renderer/gpu/command_buffer_proxy.cc
===================================================================
--- content/renderer/gpu/command_buffer_proxy.cc	(revision 119905)
+++ content/renderer/gpu/command_buffer_proxy.cc	(working copy)
@@ -392,6 +392,10 @@
   return decoder_host;
 }
 
+gpu::error::Error CommandBufferProxy::GetLastError() {
+  return last_state_.error;
+}
+
 bool CommandBufferProxy::Send(IPC::Message* msg) {
   // Caller should not intentionally send a message if the context is lost.
   DCHECK(last_state_.error == gpu::error::kNoError);