Migrate chrome/browser files to histogram_macros.h includes.

chrome/browser/mod_pagespeed/mod_pagespeed_metrics_unittest.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 "chrome/browser/mod_pagespeed/mod_pagespeed_metrics.h"
 
 #include <algorithm>
 #include <memory>
 #include <string>
 
 #include "base/memory/ref_counted.h"
-#include "base/metrics/histogram.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/statistics_recorder.h"
 #include "content/public/common/resource_type.h"
 #include "net/http/http_response_headers.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
 namespace mod_pagespeed {
 
 // Ensure that we count PageSpeed headers correctly.
@@ skipping 134 matching lines @@
   EXPECT_EQ(num_pss, server_samples->GetCount(3));
   EXPECT_EQ(num_other, server_samples->GetCount(4));
   EXPECT_EQ(num_bucket_1, version_samples->GetCount(1));
   EXPECT_EQ(num_bucket_30, version_samples->GetCount(30));
   EXPECT_EQ(num_bucket_33, version_samples->GetCount(33));
 
   headers->RemoveHeader("X-Page-Speed");
 }
 
 }  // namespace mod_pagespeed