Get maximum age of clipboard from clipboard_recent_contents.cc in iOS impl

components/open_from_clipboard/clipboard_recent_content.h

 // Copyright 2015 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 COMPONENTS_OPEN_FROM_CLIPBOARD_CLIPBOARD_RECENT_CONTENT_H_
 #define COMPONENTS_OPEN_FROM_CLIPBOARD_CLIPBOARD_RECENT_CONTENT_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 25 matching lines @@
   // Returns how old the content of the clipboard is.
   virtual base::TimeDelta GetClipboardContentAge() const = 0;
 
   // Prevent GetRecentURLFromClipboard from returning anything until the
   // clipboard's content changed.
   virtual void SuppressClipboardContent() = 0;
 
  protected:
   // GetRecentURLFromClipboard() should never return a URL from a clipboard
   // older than this.
-  const base::TimeDelta kMaximumAgeOfClipboard = base::TimeDelta::FromHours(3);
+  static base::TimeDelta MaximumAgeOfClipboard();
 
   // Returns true if the URL is appropriate to be suggested.
   static bool IsAppropriateSuggestion(const GURL& url);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ClipboardRecentContent);
 };
 
 #endif  // COMPONENTS_OPEN_FROM_CLIPBOARD_CLIPBOARD_RECENT_CONTENT_H_