Add a browsing data counter factory on iOS

ios/chrome/browser/browsing_data/ios_browsing_data_counter_factory.h

+// Copyright 2016 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 IOS_CHROME_BROWSER_BROWSING_DATA_IOS_BROWSING_DATA_COUNTER_FACTORY_H_
+#define IOS_CHROME_BROWSER_BROWSING_DATA_IOS_BROWSING_DATA_COUNTER_FACTORY_H_
+
+#include <memory>
+#include <string>
+
+#include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+
+namespace browsing_data {
+class BrowsingDataCounter;
+}
+
+class IOSBrowsingDataCounterFactory {
+ public:
+  // Creates a new instance of BrowsingDataCounter that is counting the data
+  // for |browserState|, related to a given deletion preference |pref_name|.
+  static std::unique_ptr<browsing_data::BrowsingDataCounter>
+  GetForBrowserStateAndPref(ios::ChromeBrowserState* browserState,
+                            const std::string& pref_name);

[sdefresne, 2016/09/19 17:07:53]

In browsing_data_counter_wrapper.cc you are calling this method with a "const
char*" parameter, thus allocating memory for the string. I see that in the
implementation you use std::string::operator == to compare to other "const
char*". Can you change this parameter to instead be a base::StringPiece to avoid
memory allocation?

[ioanap, 2016/09/20 09:36:48]

Done.

+
+ private:
+  IOSBrowsingDataCounterFactory();
+  ~IOSBrowsingDataCounterFactory();
+
+  DISALLOW_COPY_AND_ASSIGN(IOSBrowsingDataCounterFactory);
+};
+
+#endif  // IOS_CHROME_BROWSER_BROWSING_DATA_IOS_BROWSING_DATA_COUNTER_FACTORY_H_