Use WeakPtr for posting cc tasks to main thread

cc/scoped_thread_proxy.cc

-// Copyright 2011 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 "cc/scoped_thread_proxy.h"
-
-#include "base/bind.h"
-
-namespace cc {
-
-ScopedThreadProxy::ScopedThreadProxy(cc::Thread* targetThread)
-    : m_targetThread(targetThread)
-    , m_shutdown(false)
-{
-}
-
-ScopedThreadProxy::~ScopedThreadProxy()
-{
-}
-
-void ScopedThreadProxy::postTask(const tracked_objects::Location& location, base::Closure cb)
-{
-    m_targetThread->postTask(base::Bind(&ScopedThreadProxy::runTaskIfNotShutdown, this, cb));
-}
-
-void ScopedThreadProxy::shutdown()
-{
-    DCHECK(m_targetThread->belongsToCurrentThread());
-    DCHECK(!m_shutdown);
-    m_shutdown = true;
-}
-
-void ScopedThreadProxy::runTaskIfNotShutdown(base::Closure cb)
-{
-    // If our shutdown flag is set, it's possible that m_targetThread has already been destroyed so don't
-    // touch it.
-    if (m_shutdown) {
-        return;
-    }
-    DCHECK(m_targetThread->belongsToCurrentThread());
-    cb.Run();
-}
-
-}  // namespace cc