Add proper includes for usage of the CityHash functions.

chrome/browser/metrics/extension_metrics.cc

 // Copyright 2014 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/metrics/extension_metrics.h"
 
 #include <set>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/common/metrics/proto/system_profile.pb.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/common/extension_set.h"
-
-// From third_party/smhasher/src/City.h; that file can't be included here due
-// to macro redefinitions (of UINT8_C, etc.) on Windows.
-// TODO(mvrable): Clean up City.h so it can be included directly.
-uint64 CityHash64(const char *buf, size_t len);
+#include "third_party/smhasher/src/City.h"
 
 namespace {
 
 // The number of possible hash keys that a client may use.  The UMA client_id
 // value is reduced modulo this value to produce the key used by that
 // particular client.
 const size_t kExtensionListClientKeys = 4096;
 
 // The number of hash buckets into which extension IDs are mapped.  This sets
 // the possible output range of the HashExtension function.
@@ skipping 65 matching lines @@
   for (extensions::ExtensionSet::const_iterator it = extensions->begin();
        it != extensions->end(); ++it) {
     buckets.insert(HashExtension((*it)->id(), client_key_));
   }
 
   for (std::set<int>::const_iterator it = buckets.begin();
        it != buckets.end(); ++it) {
     system_profile->add_occupied_extension_bucket(*it);
   }
 }