Mojo Channel: Fix deferred proxy dispatch; support paused channels

ipc/ipc_channel.h

 // Copyright (c) 2012 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_CHANNEL_H_
 #define IPC_IPC_CHANNEL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 204 matching lines @@
   // Connect the pipe.  On the server side, this will initiate
   // waiting for connections.  On the client, it attempts to
   // connect to a pre-existing pipe.  Note, calling Connect()
   // will not block the calling thread and may complete
   // asynchronously.
   //
   // The subclass implementation must call WillConnect() at the beginning of its
   // implementation.
   virtual bool Connect() WARN_UNUSED_RESULT = 0;
 
+  // Similar to (and exclusive to) Connect() above, but blocks outgoing messages
+  // until a future call to Unpause().
+  //
+  // Not all implementations support ConnectPaused(). Note that this interface
+  // exists only to facilitate weird behavior where some Channel consumers want
+  // force some early messages to be transmitted before ones which were sent

[yzshen1, 2016/09/02 22:03:36]

nit: force -> to force?

[Ken Rockot(use gerrit already), 2016/09/06 17:21:27]

Done

+  // earlier. This allows that to be done without the consumer implementing
+  // their own message queueing support which may be incompatible with the
+  // Channel's internal queueing behavior.
+  virtual bool ConnectPaused() WARN_UNUSED_RESULT;
+
+  // Unpause the pipe. This allows subsequent Send() calls to transmit messages
+  // immediately, without queueing. If |flush| is true, any messages queued
+  // while paused will be flushed immediately upon unpausing. Otherwise you must
+  // call Flush() explicitly.
+  //
+  // Not all implementations support Unpause(). See ConnectPaused() above for
+  // details.
+  virtual void Unpause(bool flush);
+
+  // Manually flush the pipe. This is only useful exactly once, and only after
+  // a call to Unpause(false), in order to explicitly flush out any
+  // messages which were queued prior to unpausing.
+  //
+  // Not all implementations support Flush(). See ConnectPaused() above for
+  // details.
+  virtual void Flush();
+
   // Close this Channel explicitly.  May be called multiple times.
   // On POSIX calling close on an IPC channel that listens for connections will
   // cause it to close any accepted connections, and it will stop listening for
   // new connections. If you just want to close the currently accepted
   // connection and listen for new ones, use ResetToAcceptingConnectionState.
   virtual void Close() = 0;
 
   // Get its own process id. This value is told to the peer.
   virtual base::ProcessId GetSelfPID() const = 0;
 
@@ skipping 105 matching lines @@
 
 #if defined(OS_POSIX)
 // SocketPair() creates a pair of socket FDs suitable for using with
 // IPC::Channel.
 IPC_EXPORT bool SocketPair(int* fd1, int* fd2);
 #endif
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_H_