Add basic framework for splitting thread proxy.

cc/trees/threaded_channel.h

+// Copyright 2015 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.
+
+#ifndef CC_TREES_THREADED_CHANNEL_H_
+#define CC_TREES_THREADED_CHANNEL_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "cc/base/cc_export.h"
+#include "cc/trees/channel_impl.h"
+#include "cc/trees/channel_main.h"
+#include "cc/trees/proxy_impl.h"
+#include "cc/trees/proxy_main.h"
+#include "cc/trees/thread_proxy.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace cc {
+class ChannelImpl;
+class ChannelMain;
+class ProxyImpl;
+class ProxyMain;
+class ThreadProxy;
+
+// An implementation of ChannelMain and ChannelImpl that sends commands between

[weiliangc, 2015/09/25 19:42:46]

This comment is awesome! Thanks. :)

[Khushal, 2015/09/25 20:48:03]

Thanks! :)

+// ProxyMain and ProxyImpl across thread boundaries.
+//
+// LayerTreeHost creates ThreadedChannel and passes the ownership to ProxyMain.
+// The object life cycle and communication across threads is as follows:
+//
+//
+//           Main Thread              |               Impl Thread
+//   LayerTreeHost->InitializeProxy   |
+//               |                    |
+//        ProxyMain->Start()          |
+//               |              ThreadedChannel
+// ---------------------------------------------------------------------------
+//  ChannelMain::InitializeImpl ---PostTask---> ThreadedChannel::
+//                                                   InitializeImplOnImplThread
+//                                                          |
+//                                                   ProxyImpl::Create
+//                                                          |
+//                                                   ProxyImpl->Initialize()
+//                                                          .
+//                                                          .
+//                                          ProxyImpl::ScheduledActionBegin
+//                                                     OutputSurfaceCreation
+//                                                          |
+//                                         ChannelImpl::RequestNewOutputSurface
+// ----------------------------------------------------------------------------
+//                                                          |
+// ProxyMain->RequestNewOutputSurface()<----PostTask--------
+//              .
+//              .
+// ProxyMain->LayerTreeHostClosed
+//              |
+// ---------------------------------------------------------------------------
+// ChannelMain::SetLayerTreeClosedOnImpl---PostTask---> ProxyImpl->
+//                                                        SetLayerTreeClosed
+// ----------------------------------------------------------------------------
+
+class CC_EXPORT ThreadedChannel : public ChannelMain, public ChannelImpl {
+ public:
+  static scoped_ptr<ThreadedChannel> Create(
+      // TODO(khushalsagar): Make this ProxyMain* and write the initialization
+      // sequence. Currently ThreadProxy implements both so we pass the pointer
+      // and set ProxyImpl.
+      ThreadProxy* thread_proxy,
+      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+      scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner);
+
+  ~ThreadedChannel() override;
+
+  // ChannelMain Implementation
+  void SetThrottleFrameProductionOnImpl(bool throttle) override;
+  void SetLayerTreeHostClientReadyOnImpl() override;
+
+  // ChannelImpl Implementation
+  void DidCompleteSwapBuffers() override;
+
+ protected:
+  ThreadedChannel(ThreadProxy* thread_proxy,
+                  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+                  scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner);
+
+ private:
+  base::SingleThreadTaskRunner* MainThreadTaskRunner() const;
+  base::SingleThreadTaskRunner* ImplThreadTaskRunner() const;
+
+  ProxyMain* proxy_main_;
+
+  ProxyImpl* proxy_impl_;
+
+  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
+
+  scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadedChannel);
+};
+
+}  // namespace cc
+
+#endif  // CC_TREES_THREADED_CHANNEL_H_