Migrate content/ files to histogram_macros.h includes.

content/renderer/pepper/pepper_plugin_instance_metrics.cc

 // Copyright 2015 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.
 
 #include "content/renderer/pepper/pepper_plugin_instance_metrics.h"
 
 #include <stddef.h>
 
-#include "base/metrics/histogram.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "build/build_config.h"
 #include "ppapi/shared_impl/ppapi_preferences.h"
 
 #if defined(OS_WIN)
 #include "base/win/windows_version.h"
 #endif
 
 #define UMA_HISTOGRAM_ASPECT_RATIO(name, width, height) \
   UMA_HISTOGRAM_SPARSE_SLOWLY(                          \
@@ skipping 82 matching lines @@
   // 4 : No 3D content and GPU is blacklisted on XP
   // 5 : No 3D content and GPU is not blacklisted on XP
   // 6 : 3D content but GPU is blacklisted on XP
   // 7 : 3D content and GPU is not blacklisted on XP
   UMA_HISTOGRAM_ENUMERATION(
       "Flash.UsesGPU", is_xp * 4 + needs_gpu * 2 + prefs.is_webgl_supported, 8);
 #endif
 }
 
 }  // namespace content