Cleanup: Remove some unused code, or make them platform specific.

chrome/browser/browsing_data/browsing_data_file_system_helper.h

 // Copyright (c) 2012 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_BROWSING_DATA_BROWSING_DATA_FILE_SYSTEM_HELPER_H_
 #define CHROME_BROWSER_BROWSING_DATA_BROWSING_DATA_FILE_SYSTEM_HELPER_H_
 
 #include <list>
 #include <map>
 #include <string>
@@ skipping 126 matching lines @@
   // class. It hasn't been necessary for anything that uses the canned
   // implementation, as the canned class is only used in tests, or in read-only
   // contexts (like the non-modal cookie dialog).
   virtual void DeleteFileSystemOrigin(const GURL& origin) OVERRIDE {}
 
  private:
   // Used by Clone() to create an object without a Profile
   CannedBrowsingDataFileSystemHelper();
   virtual ~CannedBrowsingDataFileSystemHelper();
 
-  // Holds the current list of filesystems returned to the client. Access to
-  // |file_system_info_| is triggered indirectly via the UI thread and guarded
-  // by |is_fetching_|. This means |file_system_info_| is only accessed while
-  // |is_fetching_| is true. The flag |is_fetching_| is only accessed on the UI
-  // thread.
+  // Holds the current list of filesystems returned to the client.
   std::list<FileSystemInfo> file_system_info_;
 
   // The callback passed in at the beginning of the StartFetching workflow so
   // that it can be triggered via NotifyOnUIThread.
   base::Callback<void(const std::list<FileSystemInfo>&)> completion_callback_;
 
-  // Indicates whether or not we're currently fetching information: set to true
-  // when StartFetching is called on the UI thread, and reset to false when
-  // NotifyOnUIThread triggers the success callback.
-  // This property only mutates on the UI thread.
-  bool is_fetching_;
-
   DISALLOW_COPY_AND_ASSIGN(CannedBrowsingDataFileSystemHelper);
 };
 
 #endif  // CHROME_BROWSER_BROWSING_DATA_BROWSING_DATA_FILE_SYSTEM_HELPER_H_