Refactor Clipboard Last Modified Time Storage

ui/base/clipboard/clipboard.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 UI_BASE_CLIPBOARD_CLIPBOARD_H_
 #define UI_BASE_CLIPBOARD_CLIPBOARD_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 189 matching lines @@
   // Reads a bookmark from the clipboard, if available.
   virtual void ReadBookmark(base::string16* title, std::string* url) const = 0;
 
   // Reads raw data from the clipboard with the given format type. Stores result
   // as a byte vector.
   virtual void ReadData(const FormatType& format,
                         std::string* result) const = 0;
 
   // Returns an estimate of the time the clipboard was last updated.  If the
   // time is unknown, returns Time::Time().
-  virtual base::Time GetClipboardLastModifiedTime() const;
+  virtual base::Time GetLastModifiedTime() const;
+
+  // Resets the clipboard last modified time to Time::Time().
+  virtual void ClearLastModifiedTime();
 
   // Gets the FormatType corresponding to an arbitrary format string,
   // registering it with the system if needed. Due to Windows/Linux
   // limitiations, |format_string| must never be controlled by the user.
   static FormatType GetFormatType(const std::string& format_string);
 
   // Get format identifiers for various types.
   static const FormatType& GetUrlFormatType();
   static const FormatType& GetUrlWFormatType();
   static const FormatType& GetMozUrlFormatType();
@@ skipping 124 matching lines @@
 
   // Mutex that controls access to |g_clipboard_map|.
   static base::LazyInstance<base::Lock>::Leaky clipboard_map_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(Clipboard);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_CLIPBOARD_CLIPBOARD_H_