Remove IPC_BEGIN_MESSAGE_MAP_EX macro since r270839 made all bad IPCs kill their child processes.

content/browser/histogram_message_filter.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 CONTENT_BROWSER_HISTOGRAM_MESSAGE_FILTER_H_
 #define CONTENT_BROWSER_HISTOGRAM_MESSAGE_FILTER_H_
 
 #include <string>
 #include <vector>
 
 #include "content/public/browser/browser_message_filter.h"
 #include "content/public/common/process_type.h"
 
 namespace content {
 
 // This class sends and receives histogram messages in the browser process.
 class HistogramMessageFilter : public BrowserMessageFilter {
  public:
   HistogramMessageFilter();
 
   // BrowserMessageFilter implementation.
-  virtual bool OnMessageReceived(const IPC::Message& message,
-                                 bool* message_was_ok) OVERRIDE;
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
  private:
   virtual ~HistogramMessageFilter();
 
   // Message handlers.
   void OnChildHistogramData(int sequence_number,
                             const std::vector<std::string>& pickled_histograms);
   void OnGetBrowserHistogram(const std::string& name,
                              std::string* histogram_json);
 
   DISALLOW_COPY_AND_ASSIGN(HistogramMessageFilter);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_HISTOGRAM_MESSAGE_FILTER_H_