Make IPC::SyncChannel not duplicate the underlying MessageLoop implementation...

chrome/common/ipc_sync_message.h

 // Copyright (c) 2006-2008 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 CHROME_COMMON_IPC_SYNC_MESSAGE_H__
 #define CHROME_COMMON_IPC_SYNC_MESSAGE_H__
 
 #include <windows.h>
 #include <string>
 #include "base/basictypes.h"
 #include "chrome/common/ipc_message.h"
 
 namespace IPC {
 
 class MessageReplyDeserializer;
 
 class SyncMessage : public Message {
  public:
   SyncMessage(int32 routing_id, WORD type, PriorityValue priority,
               MessageReplyDeserializer* deserializer);
 
   // Call this to get a deserializer for the output parameters.
   // Note that this can only be called once, and the caller is responsible
   // for deleting the deserializer when they're done.
   MessageReplyDeserializer* GetReplyDeserializer();
 
   // If this message can cause the receiver to block while waiting for user
   // input (i.e. by calling MessageBox), then the caller needs to pump window
   // messages and dispatch asynchronous messages while waiting for the reply.
-  // If this handle is passed in, then window messages will be pumped while
-  // it's set.  The handle must be valid until after the Send call returns.
+  // If this handle is passed in, then window messages will start being pumped
+  // when it's set.  Note that this behavior will continue even if the event is
+  // later reset.  The handle must be valid until after the Send call returns.
   void set_pump_messages_event(HANDLE event) {
     pump_messages_event_ = event;
     if (event) {
       header()->flags |= PUMPING_MSGS_BIT;
     } else {
       header()->flags &= ~PUMPING_MSGS_BIT;
     }
   }
 
   // Call this if you always want to pump messages.  You can call this method
@@ skipping 37 matching lines @@
  private:
   // Derived classes need to implement this, using the given iterator (which
   // is skipped past the header for synchronous messages).
   virtual bool SerializeOutputParameters(const Message& msg, void* iter) = 0;
 };
 
 }  // namespace IPC
 
 #endif  // CHROME_COMMON_IPC_SYNC_MESSAGE_H__