Removing un-necessary conversion from std::string to base::string16.

chrome/browser/metrics/plugin_metrics_provider.h

 // 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.
 
 #ifndef CHROME_BROWSER_METRICS_PLUGIN_METRICS_PROVIDER_H_
 #define CHROME_BROWSER_METRICS_PLUGIN_METRICS_PROVIDER_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 85 matching lines @@
       const content::ChildProcessData& data) override;
   void BrowserChildProcessKilled(const content::ChildProcessData& data,
                                  int exit_code) override;
 
   PrefService* local_state_;
 
   // The list of plugins which was retrieved on the file thread.
   std::vector<content::WebPluginInfo> plugins_;
 
   // Buffer of child process notifications for quick access.
-  std::map<base::string16, ChildProcessStats> child_process_stats_buffer_;
+  std::map<std::string, ChildProcessStats> child_process_stats_buffer_;
 
   base::WeakPtrFactory<PluginMetricsProvider> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginMetricsProvider);
 };
 
 #endif  // CHROME_BROWSER_METRICS_PLUGIN_METRICS_PROVIDER_H_