Fix crash in ContextProviderMojo due to uninitialized member variable.

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/gpu/mojo_gles2_impl_autogen.h"
 #include "third_party/mojo/src/mojo/public/cpp/environment/environment.h"
 
 namespace mojo {
 
 ContextProviderMojo::ContextProviderMojo(
     ScopedMessagePipeHandle command_buffer_handle)
-    : command_buffer_handle_(command_buffer_handle.Pass()) {
+    : command_buffer_handle_(command_buffer_handle.Pass()),
+      context_(nullptr) {
   // Enabled the CHROMIUM_image extension to use GpuMemoryBuffers. The
   // implementation of which is used in CommandBufferDriver.
   capabilities_.gpu.image = true;
 }
 
 bool ContextProviderMojo::BindToCurrentThread() {
   DCHECK(command_buffer_handle_.is_valid());
   context_ = MojoGLES2CreateContext(command_buffer_handle_.release().value(),
                                     &ContextLostThunk,
                                     this,
@@ skipping 34 matching lines @@
 ContextProviderMojo::~ContextProviderMojo() {
   context_gl_.reset();
   if (context_)
     MojoGLES2DestroyContext(context_);
 }
 
 void ContextProviderMojo::ContextLost() {
 }
 
 }  // namespace mojo