Allow WebExternalTextureLayerClient to work with mailboxes.

ui/compositor/layer.cc

 // Copyright (c) 2012 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 "ui/compositor/layer.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 622 matching lines @@
 unsigned Layer::PrepareTexture(cc::ResourceUpdateQueue* queue) {
   DCHECK(texture_layer_);
   return texture_->PrepareTexture();
 }
 
 WebKit::WebGraphicsContext3D* Layer::Context3d() {
   DCHECK(texture_layer_);
   return texture_->HostContext3D();
 }
 
+bool Layer::PrepareTextureMailbox(cc::TextureMailbox* mailbox) {
+  return false;
+}
+
 void Layer::SetForceRenderSurface(bool force) {
   if (force_render_surface_ == force)
     return;
 
   force_render_surface_ = force;
   cc_layer_->SetForceRenderSurface(force_render_surface_);
 }
 
 void Layer::OnAnimationStarted(const cc::AnimationEvent& event) {
   if (animator_)
@@ skipping 278 matching lines @@
   cc_layer_->SetBounds(ConvertSizeToPixel(this, size));
 }
 
 void Layer::RecomputePosition() {
   cc_layer_->SetPosition(gfx::ScalePoint(
         gfx::PointF(bounds_.x(), bounds_.y()),
         device_scale_factor_));
 }
 
 }  // namespace ui