Revert of Remove PagePopup runtime flag (status=stable) for blink

Source/web/WebRuntimeFeatures.cpp

 /*
  * 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 162 matching lines @@
 void WebRuntimeFeatures::enableNetworkInformation(bool enable)
 {
     RuntimeEnabledFeatures::setNetworkInformationEnabled(enable);
 }
 
 void WebRuntimeFeatures::enableOrientationEvent(bool enable)
 {
     RuntimeEnabledFeatures::setOrientationEventEnabled(enable);
 }
 
+void WebRuntimeFeatures::enablePagePopup(bool enable)
+{
+    RuntimeEnabledFeatures::setPagePopupEnabled(enable);
+}
+
 void WebRuntimeFeatures::enablePeerConnection(bool enable)
 {
     RuntimeEnabledFeatures::setPeerConnectionEnabled(enable);
 }
 
 void WebRuntimeFeatures::enableRequestAutocomplete(bool enable)
 {
     RuntimeEnabledFeatures::setRequestAutocompleteEnabled(enable);
 }
 
@@ skipping 91 matching lines @@
 {
     RuntimeEnabledFeatures::setCredentialManagerEnabled(enable);
 }
 
 void WebRuntimeFeatures::enableTextBlobs(bool enable)
 {
     RuntimeEnabledFeatures::setTextBlobEnabled(enable);
 }
 
 } // namespace blink