Ensure that PP_Instance values are unique within a plugin process in addition...

content/common/child_process.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 CONTENT_COMMON_CHILD_PROCESS_H_
 #define CONTENT_COMMON_CHILD_PROCESS_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/scoped_ptr.h"
 #include "base/threading/thread.h"
 #include "base/synchronization/waitable_event.h"
 
 class ChildThread;
 
 // Base class for child processes of the browser process (i.e. renderer and
 // plugin host). This is a singleton object for each child process.
 class ChildProcess {
  public:
   // Child processes should have an object that derives from this class.
+  // Normally you would immediately call set_main_thread after construction.
   ChildProcess();
   virtual ~ChildProcess();
 
-  // Getter for the child process' main thread.
+  // May be NULL if the main thread hasn't been set explicitly.
   ChildThread* main_thread();
+
+  // Sets the object associated with the main thread of this process.
+  // Takes ownership of the pointer.
   void set_main_thread(ChildThread* thread);
 
   MessageLoop* io_message_loop() { return io_thread_.message_loop(); }
 
   // A global event object that is signalled when the main thread's message
   // loop exits.  This gives background threads a way to observe the main
   // thread shutting down.  This can be useful when a background thread is
   // waiting for some information from the browser process.  If the browser
   // process goes away prematurely, the background thread can at least notice
   // the child processes's main thread exiting to determine that it should give
@@ skipping 27 matching lines @@
   // io_thread_.
   scoped_ptr<ChildThread> main_thread_;
 
   // The singleton instance for this process.
   static ChildProcess* child_process_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildProcess);
 };
 
 #endif  // CONTENT_COMMON_CHILD_PROCESS_H_