g++ 4.3.x doesn't seem to like forward declarations...

chrome/browser/renderer_host/async_resource_handler.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_BROWSER_RENDERER_HOST_ASYNC_RESOURCE_HANDLER_H_
 #define CHROME_BROWSER_RENDERER_HOST_ASYNC_RESOURCE_HANDLER_H_
 
 #include "base/process.h"
 #include "chrome/browser/renderer_host/resource_dispatcher_host.h"
 #include "chrome/browser/renderer_host/resource_handler.h"
 
-class base::SharedMemory;
+namespace base {
+  class SharedMemory;
+}
 
 // Used to complete an asynchronous resource request in response to resource
 // load events from the resource dispatcher host.
 class AsyncResourceHandler : public ResourceHandler {
  public:
   AsyncResourceHandler(ResourceDispatcherHost::Receiver* receiver,
                        int render_process_host_id,
                        int routing_id,
                        base::ProcessHandle render_process,
                        const GURL& url,
@@ skipping 19 matching lines @@
   ResourceDispatcherHost::Receiver* receiver_;
   int render_process_host_id_;
   int routing_id_;
   base::ProcessHandle render_process_;
   ResourceDispatcherHost* rdh_;
 
   DISALLOW_COPY_AND_ASSIGN(AsyncResourceHandler);
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_ASYNC_RESOURCE_HANDLER_H_