Enable the Sky compositor again

sky/compositor/surface_holder.cc

 // Copyright 2014 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 "sky/compositor/surface_holder.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "mojo/converters/geometry/geometry_type_converters.h"
 #include "mojo/public/cpp/application/connect.h"
@@ skipping 10 matching lines @@
   mojo::ServiceProviderPtr service_provider;
   shell->ConnectToApplication("mojo:surfaces_service",
                               mojo::GetProxy(&service_provider));
   mojo::ConnectToService(service_provider.get(), &surfaces_service_);
 
   surfaces_service_->CreateSurfaceConnection(base::Bind(
       &SurfaceHolder::OnSurfaceConnectionCreated, weak_factory_.GetWeakPtr()));
 }
 
 SurfaceHolder::~SurfaceHolder() {
-  if (surface_id_)
+  if (surface_ && surface_id_)
     surface_->DestroySurface(surface_id_.Clone());
 }
 
+bool SurfaceHolder::IsReadyForFrame() const {
+  return surface_;
+}
+
 void SurfaceHolder::SubmitFrame(mojo::FramePtr frame) {
   surface_->SubmitFrame(surface_id_.Clone(), frame.Pass());
 }
 
 void SurfaceHolder::SetSize(const gfx::Size& size) {
   if (surface_id_ && size_ == size)
     return;
 
   if (surface_id_) {
     surface_->DestroySurface(surface_id_.Clone());
@@ skipping 17 matching lines @@
 }
 
 void SurfaceHolder::OnSurfaceConnectionCreated(mojo::SurfacePtr surface,
                                                uint32_t id_namespace) {
   surface_ = surface.Pass();
   surface_.set_client(this);
   surface_allocator_.reset(new SurfaceAllocator(id_namespace));
 }
 
 }  // namespace sky