Add unittest to Open from Clipboard component.

components/open_from_clipboard/clipboard_recent_content_ios.h

Index: components/open_from_clipboard/clipboard_recent_content_ios.h
diff --git a/components/open_from_clipboard/clipboard_recent_content_ios.h b/components/open_from_clipboard/clipboard_recent_content_ios.h
index 062d0f1b6917b668851f0d9bd9bedec5adfbff6d..174166de924a3c03ea3d2f287102d9eaf958a93f 100644
--- a/components/open_from_clipboard/clipboard_recent_content_ios.h
+++ b/components/open_from_clipboard/clipboard_recent_content_ios.h
@@ -12,6 +12,10 @@
 @class NSDate;
 @class PasteboardNotificationListenerBridge;
 
+namespace test {
+class ClipboardRecentContentIOSTestHelper;
+}
+
 template <typename T>
 struct DefaultSingletonTraits;
 
@@ -25,11 +29,15 @@ class ClipboardRecentContentIOS : public ClipboardRecentContent {
   // 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.