Allow proxy channels to be created without initializing the underlying channel.

ipc/ipc_sync_channel.h

 // Copyright (c) 2011 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 IPC_IPC_SYNC_SENDER_H__
 #define IPC_IPC_SYNC_SENDER_H__
 #pragma once
 
 #include <string>
 #include <deque>
@@ skipping 45 matching lines @@
 // be dispatched in a reentrant manner to avoid deadlock.
 //
 //
 // Note that care must be taken that the lifetime of the ipc_thread argument
 // is more than this object.  If the message loop goes away while this object
 // is running and it's used to send a message, then it will use the invalid
 // message loop pointer to proxy it to the ipc thread.
 class IPC_EXPORT SyncChannel : public ChannelProxy,
                                public base::WaitableEventWatcher::Delegate {
  public:
+  // Creates and initializes a sync channel. If create_pipe_now is specified,
+  // the channel will be initialized synchronously.
   SyncChannel(const IPC::ChannelHandle& channel_handle,
               Channel::Mode mode,
               Channel::Listener* listener,
               base::MessageLoopProxy* ipc_message_loop,
               bool create_pipe_now,
               base::WaitableEvent* shutdown_event);
+
+  // Creates an uninitialized sync channel. Call ChannelProxy::Init to
+  // initialize the channel. This two-step setup allows message filters to be
+  // added before any messages are sent or received.
+  SyncChannel(Channel::Listener* listener,
+              base::MessageLoopProxy* ipc_message_loop,
+              base::WaitableEvent* shutdown_event);
+
   virtual ~SyncChannel();
 
   virtual bool Send(Message* message);
   virtual bool SendWithTimeout(Message* message, int timeout_ms);
 
   // Whether we allow sending messages with no time-out.
   void set_sync_messages_with_no_timeout_allowed(bool value) {
     sync_messages_with_no_timeout_allowed_ = value;
   }
 
@@ skipping 109 matching lines @@
 
   // Used to signal events between the IPC and listener threads.
   base::WaitableEventWatcher dispatch_watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncChannel);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_SENDER_H__