Don't use any member variables when sending a sync call...

ipc/ipc_sync_channel.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 IPC_IPC_SYNC_SENDER_H__
 #define IPC_IPC_SYNC_SENDER_H__
 
 #include <string>
 #include <deque>
 
@@ skipping 127 matching lines @@
  private:
   // WaitableEventWatcher::Delegate implementation.
   virtual void OnWaitableEventSignaled(base::WaitableEvent* arg);
 
   SyncContext* sync_context() {
     return reinterpret_cast<SyncContext*>(context());
   }
 
   // Both these functions wait for a reply, timeout or process shutdown.  The
   // latter one also runs a nested message loop in the meantime.
-  void WaitForReply(base::WaitableEvent* pump_messages_event);
+  static void WaitForReply(
+      SyncContext* context, base::WaitableEvent* pump_messages_event);
 
   // Runs a nested message loop until a reply arrives, times out, or the process
   // shuts down.
-  void WaitForReplyWithNestedMessageLoop();
+  static void WaitForReplyWithNestedMessageLoop(SyncContext* context);
 
   bool sync_messages_with_no_timeout_allowed_;
 
   // Used to signal events between the IPC and listener threads.
   base::WaitableEventWatcher dispatch_watcher_;
 
   DISALLOW_EVIL_CONSTRUCTORS(SyncChannel);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_SENDER_H__