Use lock-free lazy initialization for static histogram references

chrome/renderer/renderer_main.cc

 // 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.
 
 #if defined(OS_MACOSX)
 #include <signal.h>
 #include <unistd.h>
 #endif  // OS_MACOSX
 
 #include "base/command_line.h"
@@ skipping 179 matching lines @@
     begin_process_message_ = base::TimeTicks::Now();
   }
 
   virtual void DidProcessTask(const Task* task) {
     if (begin_process_message_ != base::TimeTicks())
       process_times_->AddTime(base::TimeTicks::Now() - begin_process_message_);
   }
 
  private:
   base::TimeTicks begin_process_message_;
-  scoped_refptr<base::Histogram> process_times_;
+  base::Histogram* const process_times_;
   DISALLOW_COPY_AND_ASSIGN(RendererMessageLoopObserver);
 };
 
 // mainline routine for running as the Renderer process
 int RendererMain(const MainFunctionParams& parameters) {
   TRACE_EVENT_BEGIN("RendererMain", 0, "");
 
   const CommandLine& parsed_command_line = parameters.command_line_;
   base::mac::ScopedNSAutoreleasePool* pool = parameters.autorelease_pool_;
 
@@ skipping 118 matching lines @@
         pool->Recycle();
       TRACE_EVENT_BEGIN("RendererMain.START_MSG_LOOP", 0, 0);
       MessageLoop::current()->Run();
       TRACE_EVENT_END("RendererMain.START_MSG_LOOP", 0, 0);
     }
   }
   platform.PlatformUninitialize();
   TRACE_EVENT_END("RendererMain", 0, "");
   return 0;
 }