Add runtime flag for PagePopup.

Source/WebKit/chromium/public/WebRuntimeFeatures.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 127 matching lines @@
 
     WEBKIT_EXPORT static void enableWebKitMediaSource(bool);
     WEBKIT_EXPORT static bool isWebKitMediaSourceEnabled();
 
     WEBKIT_EXPORT static void enableMediaStream(bool);
     WEBKIT_EXPORT static bool isMediaStreamEnabled();
 
     WEBKIT_EXPORT static void enableNotifications(bool);
     WEBKIT_EXPORT static bool isNotificationsEnabled();
 
+    WEBKIT_EXPORT static void enablePagePopup(bool);
+    WEBKIT_EXPORT static bool isPagePopupEnabled();
+
     WEBKIT_EXPORT static void enablePeerConnection(bool);
     WEBKIT_EXPORT static bool isPeerConnectionEnabled();
 
     WEBKIT_EXPORT static void enableQuota(bool);
     WEBKIT_EXPORT static bool isQuotaEnabled();
 
     WEBKIT_EXPORT static void enableRequestAutocomplete(bool);
     WEBKIT_EXPORT static bool isRequestAutocompleteEnabled();
 
     WEBKIT_EXPORT static void enableScriptedSpeech(bool);
@@ skipping 29 matching lines @@
     WEBKIT_EXPORT static void enableWebPInAcceptHeader(bool);
     WEBKIT_EXPORT static bool isWebPInAcceptHeaderEnabled();
 
 private:
     WebRuntimeFeatures();
 };
 
 } // namespace WebKit
 
 #endif