Have srcset respond to viewport changes

Source/core/loader/ImageLoader.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 57 matching lines @@
         ForceLoadImmediately
     };
 
     enum UpdateFromElementBehavior {
         // This should be the update behavior when the element is attached to a document, or when DOM mutations trigger a new load.
         // Starts loading if a load hasn't already been started.
         UpdateNormal,
         // This should be the update behavior when the resource was changed (via 'src', 'srcset' or 'sizes').
         // Starts a new load even if a previous load of the same resource have failed, to match Firefox's behavior.
         // FIXME - Verify that this is the right behavior according to the spec.
-        UpdateIgnorePreviousError
+        UpdateIgnorePreviousError,
+        // This forces the image to update its intrinsic size, even if the image source has not changed.
+        UpdateForce
     };
 
     enum BypassMainWorldBehavior {
         BypassMainWorldCSP,
         DoNotBypassMainWorldCSP
     };
 
     void updateFromElement(UpdateFromElementBehavior = UpdateNormal, LoadType = LoadNormally);
 
     void elementDidMoveToNewDocument();
@@ skipping 22 matching lines @@
     void addClient(ImageLoaderClient*);
     void removeClient(ImageLoaderClient*);
 
 protected:
     virtual void notifyFinished(Resource*) OVERRIDE;
 
 private:
     class Task;
 
     // Called from the task or from updateFromElement to initiate the load.
-    void doUpdateFromElement(BypassMainWorldBehavior);
+    void doUpdateFromElement(BypassMainWorldBehavior, UpdateFromElementBehavior);
 
     virtual void dispatchLoadEvent() = 0;
     virtual String sourceURI(const AtomicString&) const = 0;
 
     void updatedHasPendingEvent();
 
     void dispatchPendingLoadEvent();
     void dispatchPendingErrorEvent();
 
     RenderImageResource* renderImageResource();
     void updateRenderer();
 
     void setImageWithoutConsideringPendingLoadEvent(ImageResource*);
     void sourceImageChanged();
     void clearFailedLoadURL();
     void crossSiteOrCSPViolationOccured(AtomicString);
-    void enqueueImageLoadingMicroTask();
+    void enqueueImageLoadingMicroTask(UpdateFromElementBehavior);
     static ResourcePtr<ImageResource> createImageResourceForImageDocument(Document&, FetchRequest&);
 
     void timerFired(Timer<ImageLoader>*);
 
     KURL imageSourceToKURL(AtomicString) const;
 
     // Used to determine whether to immediately initiate the load
     // or to schedule a microtask.
     bool shouldLoadImmediately(const KURL&, LoadType) const;
 
@@ skipping 34 matching lines @@
     bool m_hasPendingErrorEvent : 1;
     bool m_imageComplete : 1;
     bool m_loadingImageDocument : 1;
     bool m_elementIsProtected : 1;
     unsigned m_highPriorityClientCount;
 };
 
 }
 
 #endif