Remove StaleWhileRevalidateCacheControl feature.

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 291 matching lines @@
 void WebRuntimeFeatures::enablePushMessaging(bool enable)
 {
     RuntimeEnabledFeatures::setPushMessagingEnabled(enable);
 }
 
 void WebRuntimeFeatures::enablePushMessagingData(bool enable)
 {
     RuntimeEnabledFeatures::setPushMessagingDataEnabled(enable);
 }
 
-void WebRuntimeFeatures::enableStaleWhileRevalidateCacheControl(bool enable)
-{
-    RuntimeEnabledFeatures::setStaleWhileRevalidateCacheControlEnabled(enable);
-}
-
 void WebRuntimeFeatures::enableUnsafeES3APIs(bool enable)
 {
     RuntimeEnabledFeatures::setUnsafeES3APIsEnabled(enable);
 }
 
 void WebRuntimeFeatures::enableWebVR(bool enable)
 {
     RuntimeEnabledFeatures::setWebVREnabled(enable);
 }
 
 void WebRuntimeFeatures::enableNewMediaPlaybackUi(bool enable)
 {
     RuntimeEnabledFeatures::setNewMediaPlaybackUiEnabled(enable);
 }
 
 void WebRuntimeFeatures::enablePresentationAPI(bool enable)
 {
     RuntimeEnabledFeatures::setPresentationEnabled(enable);
 }
 
 } // namespace blink