Add unittest to Open from Clipboard component.

components/open_from_clipboard/clipboard_recent_content_ios.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_IOS_H_
 #define COMPONENTS_OPEN_FROM_CLIPBOARD_CLIPBOARD_RECENT_CONTENT_IOS_H_
 
 #include "base/mac/scoped_nsobject.h"
 #include "components/open_from_clipboard/clipboard_recent_content.h"
 #include "url/gurl.h"
 
 @class NSDate;
 @class PasteboardNotificationListenerBridge;
 
+namespace test {
+class ClipboardRecentContentIOSTestHelper;
+}
+
 template <typename T>
 struct DefaultSingletonTraits;
 
 // IOS implementation of ClipboardRecentContent
 class ClipboardRecentContentIOS : public ClipboardRecentContent {
  public:
   static ClipboardRecentContentIOS* GetInstance();
   // Notifies that the content of the pasteboard may have changed.
   void PasteboardChanged();
 
   // ClipboardRecentContent implementation.
   bool GetRecentURLFromClipboard(GURL* url) const override;
 
+ protected:
+  // Protected for testing.
+  ClipboardRecentContentIOS();
+  ~ClipboardRecentContentIOS() override;
+
  private:
   friend struct DefaultSingletonTraits<ClipboardRecentContentIOS>;
+  friend class test::ClipboardRecentContentIOSTestHelper;
 
-  ClipboardRecentContentIOS();
-  ~ClipboardRecentContentIOS() override;
   // Loads information from the user defaults about the latest pasteboard entry.
   void LoadFromUserDefaults();
   // Saves information to the user defaults about the latest pasteboard entry.
   void SaveToUserDefaults();
   // Returns the URL contained in the clipboard (if any).
   GURL URLFromPasteboard();
   // Returns whether the device has restarted since the last time a pasteboard
   // change was detected.
   bool DeviceRestartedSincePasteboardChanged();
 
   // The pasteboard's change count. Increases everytime the pasteboard changes.
   NSInteger lastPasteboardChangeCount_;
   // Estimation of the date when the pasteboard changed.
   base::scoped_nsobject<NSDate> lastPasteboardChangeDate_;
   // Cache of the GURL contained in the pasteboard (if any).
   GURL urlFromPasteboardCache_;
   // Bridge to receive notification when the pasteboard changes.
   base::scoped_nsobject<PasteboardNotificationListenerBridge>
       notificationBridge_;
 
   DISALLOW_COPY_AND_ASSIGN(ClipboardRecentContentIOS);
 };
 
 #endif  // COMPONENTS_OPEN_FROM_CLIPBOARD_CLIPBOARD_RECENT_CONTENT_IOS_H_