Deliver IPC messages together with SwapCompositorFrame

content/renderer/gpu/frame_swap_message_queue.h

+// 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.
+
+#ifndef CONTENT_RENDERER_GPU_FRAME_SWAP_MESSAGE_QUEUE_H_
+#define CONTENT_RENDERER_GPU_FRAME_SWAP_MESSAGE_QUEUE_H_
+
+#include <map>
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+#include "content/common/content_export.h"
+
+namespace IPC {
+class Message;
+};
+
+namespace content {
+
+// Queue used to keep track of which IPC::Messages should be sent along with a
+// particular compositor frame swap.
+class CONTENT_EXPORT FrameSwapMessageQueue :
+    public base::RefCountedThreadSafe<FrameSwapMessageQueue> {
+ public:
+  typedef scoped_ptr<base::AutoLock> SendMessageScope;
+  FrameSwapMessageQueue();
+
+  // Queues message to be sent on next drain.
+  //
+  // |msg| - message to queue. The method takes ownership of |msg|.
+  void QueueMessage(IPC::Message* msg);
+
+  // Queues message to take place on next drain coresponding to the given
+  // source_frame_number. Takes ownership of |msg|.
+  //
+  // |source_frame_number| frame number to queue |msg| for.
+  // |msg| - message to queue. The method takes ownership of |msg|.
+  // Returns false if the given source frame number had already been drained at
+  // least once.
+  bool TryQueueMessage(int source_frame_number, IPC::Message* msg);
+
+  // SendMessageScope must exist till after the messages are sent. The
+  // SendMessageScope is used to make sure that messages sent directly from the
+  // main thread can't overtake the message containing |messages|.
+  //
+  // |source_frame_number| frame number to get messages for
+  // |messages| vector to store messages. it's not cleared, only appended to.
+  //            The method will append messages queued for frame numbers lower
+  //            or equal to |source_frame_number|
+  // Returns an object that must be kept in scope till an IPC message containing
+  // |messages| is sent.
+  SendMessageScope DrainMessages(int source_frame_number,
+                                 std::vector<IPC::Message>* messages);
+
+ private:
+  friend class base::RefCountedThreadSafe<FrameSwapMessageQueue>;
+  typedef std::map<int, std::vector<IPC::Message*> > FrameQueueMap;
+
+  static void TransferMessages(std::vector<IPC::Message*>& source,
+                               std::vector<IPC::Message>* dest);
+
+  ~FrameSwapMessageQueue();
+
+  base::Lock lock_;
+  int highest_swapped_source_frame_number_;
+  FrameQueueMap queued_messages_;
+
+  DISALLOW_COPY_AND_ASSIGN(FrameSwapMessageQueue);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_GPU_FRAME_SWAP_MESSAGE_QUEUE_H_