Implement Discard and EnsureBackbufferCHROMIUM using command buffer instead of IPC.

content/common/gpu/client/command_buffer_proxy_impl.cc

Index: content/common/gpu/client/command_buffer_proxy_impl.cc
diff --git a/content/common/gpu/client/command_buffer_proxy_impl.cc b/content/common/gpu/client/command_buffer_proxy_impl.cc
index fa6c25ff779d8c32972fd50d8f22ad9e67b6d2b6..fd57d2fb55080148f669c98c0c4bea728358fed0 100644
--- a/content/common/gpu/client/command_buffer_proxy_impl.cc
+++ b/content/common/gpu/client/command_buffer_proxy_impl.cc
@@ -376,20 +376,6 @@ bool CommandBufferProxyImpl::SetSurfaceVisible(bool visible) {
   return Send(new GpuCommandBufferMsg_SetSurfaceVisible(route_id_, visible));
 }
 
-bool CommandBufferProxyImpl::DiscardBackbuffer() {
-  if (last_state_.error != gpu::error::kNoError)
-    return false;
-
-  return Send(new GpuCommandBufferMsg_DiscardBackbuffer(route_id_));
-}
-
-bool CommandBufferProxyImpl::EnsureBackbuffer() {
-  if (last_state_.error != gpu::error::kNoError)
-    return false;
-
-  return Send(new GpuCommandBufferMsg_EnsureBackbuffer(route_id_));
-}
-
 bool CommandBufferProxyImpl::SetParent(
     CommandBufferProxy* parent_command_buffer,
     uint32 parent_texture_id) {