Deliver IPC messages together with SwapCompositorFrame

content/renderer/gpu/frame_swap_message_queue.h

Index: content/renderer/gpu/frame_swap_message_queue.h
diff --git a/content/renderer/gpu/frame_swap_message_queue.h b/content/renderer/gpu/frame_swap_message_queue.h
new file mode 100644
index 0000000000000000000000000000000000000000..5cf37c53ac46d9eaa0e1ecdf9c389582df9fbbc0
--- /dev/null
+++ b/content/renderer/gpu/frame_swap_message_queue.h
@@ -0,0 +1,92 @@
+// 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/auto_reset.h"
+#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:
+  class CONTENT_EXPORT SendMessageScope {
+   public:
+    virtual ~SendMessageScope() {}
+  };
+
+  FrameSwapMessageQueue();
+
+  // Queues message to be returned on the next call to DrainMessages.
+  //
+  // |msg| - message to queue. The method takes ownership of |msg|.
+  void QueueMessage(IPC::Message* msg);
+
+  // Queues message to be returned on the first call to DrainMessages ocurring
+  // after a DidSwapFrame call with the coresponding source_frame_number. Takes
+  // ownership of |msg|.

[piman, 2014/06/19 23:02:29]

nit: pass scoped_ptr<IPC::Message> to be explicit about it?

[mkosiba (inactive), 2014/06/24 18:29:54]

Done.

+  //
+  // |source_frame_number| frame number to queue |msg| for.
+  // |msg| - message to queue. The method takes ownership of |msg|.
+  // |is_first| - output parameter. Set to true if this was the first message
+  //              enqueued for the given source_frame_number.
+  void QueueMessage(int source_frame_number, IPC::Message* msg, bool* is_first);

[piman, 2014/06/19 23:02:29]

nit: no overloading... QueueMessageForFrame ?

[mkosiba (inactive), 2014/06/24 18:29:54]

Done.

+
+  // Returns true if there are no messages in the queue.
+  bool Empty() const;
+
+  // Makes the next call do DrainMessages return messages scheduled for any
+  // source frame numbers less than or equal to |source_frame_number|.
+  void AdvanceToFrame(int source_frame_number);
+
+  // A SendMessageScope object must be held by the caller when this method is
+  // called.
+  //
+  // |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|
+  void DrainMessages(std::vector<IPC::Message>* messages);
+  void DrainMessages(std::vector<IPC::Message*>* messages);

[piman, 2014/06/19 23:02:29]

nit: no overloading.

For the second version, it would be useful to specify that the caller takes
ownership of the messages. Maybe use a ScopedVector?


Maybe you can just remove the first version, it's called at only one place, and
you could move the TransferMessages logic there (or leave it as a public helper
method).

[mkosiba (inactive), 2014/06/24 18:29:54]

Done.

+
+  // SendMessageScope is used to make sure that messages sent from different
+  // threads (impl/main) are scheduled in the right order on the IO threads.
+  //
+  // Returns an object that must be kept in scope till an IPC message containing
+  // |messages| is sent.
+  scoped_ptr<SendMessageScope> AcquireSendMessageScope();
+
+ 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();
+
+  mutable base::Lock lock_;
+  int highest_swapped_source_frame_number_;
+  FrameQueueMap queued_messages_;
+  std::vector<IPC::Message*> next_drain_messages_;
+
+  DISALLOW_COPY_AND_ASSIGN(FrameSwapMessageQueue);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_GPU_FRAME_SWAP_MESSAGE_QUEUE_H_