Fix compositor integration in ui/compositor

mojo/cc/context_provider_mojo.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 "mojo/cc/context_provider_mojo.h"
 
 #include "base/logging.h"
 #include "mojo/public/cpp/environment/environment.h"
 
 namespace mojo {
 
 ContextProviderMojo::ContextProviderMojo(
     ScopedMessagePipeHandle command_buffer_handle)
     : command_buffer_handle_(command_buffer_handle.Pass()),
+      context_(nullptr),
       context_lost_(false) {
 }
 
 bool ContextProviderMojo::BindToCurrentThread() {
   DCHECK(command_buffer_handle_.is_valid());
   context_ = MojoGLES2CreateContext(command_buffer_handle_.release().value(),
                                     &ContextLostThunk,
                                     this,
                                     Environment::GetDefaultAsyncWaiter());
   return !!context_;
 }
 
 gpu::gles2::GLES2Interface* ContextProviderMojo::ContextGL() {
   if (!context_)
-    return NULL;
+    return nullptr;
   return static_cast<gpu::gles2::GLES2Interface*>(
       MojoGLES2GetGLES2Interface(context_));
 }
 
 gpu::ContextSupport* ContextProviderMojo::ContextSupport() {
   if (!context_)
-    return NULL;
+    return nullptr;
   return static_cast<gpu::ContextSupport*>(
       MojoGLES2GetContextSupport(context_));
 }
 
 class GrContext* ContextProviderMojo::GrContext() { return NULL; }
 
 cc::ContextProvider::Capabilities ContextProviderMojo::ContextCapabilities() {
   return capabilities_;
 }
 
 bool ContextProviderMojo::IsContextLost() {
   return context_lost_;
 }
 bool ContextProviderMojo::DestroyedOnMainThread() { return !context_; }
 
 ContextProviderMojo::~ContextProviderMojo() {
   if (context_)
     MojoGLES2DestroyContext(context_);
 }
 
 void ContextProviderMojo::ContextLost() {
   context_lost_ = true;
 }
 
 }  // namespace mojo