ChannelProxy: Send() from UI thread when ChannelMojo is used.

ipc/mojo/ipc_channel_mojo.h

Index: ipc/mojo/ipc_channel_mojo.h
diff --git a/ipc/mojo/ipc_channel_mojo.h b/ipc/mojo/ipc_channel_mojo.h
index 1ef32c6bf2704e7f796b77dcdd2bff3b648662e8..db4277e70b66ee9737a1d052165db7c268483d4c 100644
--- a/ipc/mojo/ipc_channel_mojo.h
+++ b/ipc/mojo/ipc_channel_mojo.h
@@ -10,6 +10,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
+#include "base/synchronization/lock.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_channel_factory.h"
 #include "ipc/ipc_export.h"
@@ -86,6 +87,7 @@ class IPC_MOJO_EXPORT ChannelMojo
   bool Connect() override;
   void Close() override;
   bool Send(Message* message) override;
+  bool IsSendThreadSafe() const override;
   base::ProcessId GetPeerPID() const override;
   base::ProcessId GetSelfPID() const override;
 
@@ -135,15 +137,22 @@ class IPC_MOJO_EXPORT ChannelMojo
   typedef internal::MessagePipeReader::DelayedDeleter ReaderDeleter;
 
   void InitDelegate(ChannelMojo::Delegate* delegate);
+  base::TaskRunner* GetIOTaskRunner();
 
   scoped_ptr<MojoBootstrap> bootstrap_;
-  base::WeakPtr<Delegate> delegate_;
   Mode mode_;
   Listener* listener_;
   base::ProcessId peer_pid_;
   scoped_ptr<mojo::embedder::ChannelInfo,
              ChannelInfoDeleter> channel_info_;
 
+  // Guards |message_reader_|, |pending_messages_| and |delegate_|.
+  //
+  // * The contents of |pending_messages_| can be modified from any threads.
+  // * |delegate_| and |message_reader_| is modified only from IO thread,
+  //   but they can be referred from other threads.
+  base::Lock lock_;
+  base::WeakPtr<Delegate> delegate_;
   scoped_ptr<internal::MessagePipeReader, ReaderDeleter> message_reader_;
   ScopedVector<Message> pending_messages_;