Add ChildMessageFilter, a base class for renderer/worker cross-thread MessageFilter

content/child/cross_thread_message_filter.h

Index: content/child/cross_thread_message_filter.h
diff --git a/content/child/cross_thread_message_filter.h b/content/child/cross_thread_message_filter.h
new file mode 100644
index 0000000000000000000000000000000000000000..27391e0537bb6adcdb8cd8186cc8aa6f84074296
--- /dev/null
+++ b/content/child/cross_thread_message_filter.h
@@ -0,0 +1,60 @@
+// Copyright 2013 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_CHILD_CROSS_THREAD_MESSAGE_FILTER_H_
+#define CONTENT_CHILD_CROSS_THREAD_MESSAGE_FILTER_H_
+
+#include "ipc/ipc_channel_proxy.h"
+
+namespace content {
+
+// A base class of cross-thread message filter for dispatching messages
+// to blink's worker threads via WorkerTaskRunner.

[jam, 2013/11/08 19:51:59]

nit: no need to mention blink here, this class can be used to service any thread
other than the main

[kinuko, 2013/11/15 14:40:36]

Done.

+class CrossThreadMessageFilter

[jam, 2013/11/08 19:51:59]

nit: I think ChildMessageFilter is sufficient, that would match
BrowserMessageFilter

[kinuko, 2013/11/15 14:40:36]

Ok, done. (scherkus@, hope it's ok that I'm stealing your CL now)

[scherkus (not reviewing), 2013/11/15 19:12:19]

go for it! I don't have the bandwidth at the moment to tackle it :)

+    : public base::RefCountedThreadSafe<CrossThreadMessageFilter> {
+ public:
+  // If implementors want to run OnMessageReceived on a different thread
+  // it should set |thread_id| to a thee thread ID and return true.
+  // 0 thread_id indicates OnMessageReceived should be dispatched to
+  // the main child thread.
+  // Returning false indicates OnMessageReceived should be called on the
+  // IPC thread.
+  virtual bool OverrideThreadIDForMessage(
+      const IPC::Message& msg,
+      int* thread_id) = 0;
+
+  // If OverrideThreadIDForMessage returned true this is called on the
+  // target thread that is returned by OverrideThreadIDForMessage.
+  virtual bool OnMessageReceived(const IPC::Message& msg) = 0;
+
+  // This method is called when WorkerTaskRunner::PostTask() returned false
+  // for the target thread.  Note that there's still a listtle chance that
+  // PostTask() returns true but OnMessageReceivedOnTargetThread() is
+  // never called.  By default this does nothing.
+  virtual void OnStaleMessageReceived(const IPC::Message& msg) {}

[jam, 2013/11/08 19:51:59]

can you also add a Send() method, i.e. see
https://codereview.chromium.org/24636002/diff/16001/content/child/child_messa...

[kinuko, 2013/11/15 14:40:36]

Done.

+
+ protected:
+  CrossThreadMessageFilter();
+  virtual ~CrossThreadMessageFilter();
+
+ private:
+  class Internal;
+  friend class ChildThread;
+  friend class RenderThreadImpl;
+  friend class WorkerThread;
+
+  friend class base::RefCountedThreadSafe<CrossThreadMessageFilter>;
+
+  IPC::ChannelProxy::MessageFilter* GetFilter();
+
+  // This implements IPC::ChannelProxy::MessageFilter to hide the actual
+  // filter methods from child classes.
+  Internal* internal_;
+
+  DISALLOW_COPY_AND_ASSIGN(CrossThreadMessageFilter);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_CHILD_CROSS_THREAD_MESSAGE_FILTER_H_