Call media query change listeners asynchronously.

Source/core/css/MediaQueryList.h

 /*
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  *  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.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 21 matching lines @@
 class MediaQueryMatcher;
 class MediaQuerySet;
 
 // MediaQueryList interface is specified at http://dev.w3.org/csswg/cssom-view/#the-mediaquerylist-interface
 // The objects of this class are returned by window.matchMedia. They may be used to
 // retrieve the current value of the given media query and to add/remove listeners that
 // will be called whenever the value of the query changes.
 
 class MediaQueryList FINAL : public RefCountedWillBeGarbageCollectedFinalized<MediaQueryList> {
 public:
+    class Listener : public RefCountedWillBeGarbageCollectedFinalized<Listener> {

[esprehn, 2014/07/01 00:01:06]

This virtual abstraction seems like it could be a separate patch from the timing
change.

[cbiesinger, 2014/07/01 00:12:09]

It could. Want me to do that?

+    public:
+        virtual ~Listener() { }
+        virtual void mediaQueryChanged() = 0;
+        virtual bool equals(Listener* other) { return this == other; }

[esprehn, 2014/07/01 00:01:06]

This shouldn't need to be virtual.

[cbiesinger, 2014/07/01 00:12:09]

How so? The implementation for JS listeners needs to use
ScriptValue::operator==, whereas the C++ implementation needs pointer equality.

+
+        virtual MediaQueryListListener* isMediaQueryListListener() { return nullptr; }
+
+        // Used to keep the MediaQueryList alive and registered with the MediaQueryMatcher
+        // as long as the listener exists.
+        void setMediaQueryList(MediaQueryList* query) { m_query = query; }
+        void clearMediaQueryList() { m_query = nullptr; }
+
+        void trace(Visitor* visitor) { visitor->trace(m_query); }
+    protected:
+        RefPtrWillBeMember<MediaQueryList> m_query;
+    };
+
     static PassRefPtrWillBeRawPtr<MediaQueryList> create(PassRefPtrWillBeRawPtr<MediaQueryMatcher>, PassRefPtrWillBeRawPtr<MediaQuerySet>);
     virtual ~MediaQueryList();
 
     String media() const;
     bool matches();
 
-    void addListener(PassRefPtrWillBeRawPtr<MediaQueryListListener>);
-    void removeListener(PassRefPtrWillBeRawPtr<MediaQueryListListener>);
+    // These listeners will be called at requestAnimationFrame time.
+    void addListener(PassRefPtrWillBeRawPtr<Listener>);
+    void removeListener(PassRefPtrWillBeRawPtr<Listener>);
 
-    void mediaFeaturesChanged(WillBeHeapVector<RefPtrWillBeMember<MediaQueryListListener> >* toNotify);
+    void mediaFeaturesChanged(WillBeHeapVector<RefPtrWillBeMember<Listener> >* listenersToNotify);
 
     void trace(Visitor*);
 
     void documentDetached();
 
 private:
     MediaQueryList(PassRefPtrWillBeRawPtr<MediaQueryMatcher>, PassRefPtrWillBeRawPtr<MediaQuerySet>);
 
     bool updateMatches();
 
     RefPtrWillBeMember<MediaQueryMatcher> m_matcher;
     RefPtrWillBeMember<MediaQuerySet> m_media;
-    typedef WillBeHeapListHashSet<RefPtrWillBeMember<MediaQueryListListener> > ListenerList;
+    typedef WillBeHeapListHashSet<RefPtrWillBeMember<Listener> > ListenerList;
     ListenerList m_listeners;
     bool m_matchesDirty;
     bool m_matches;
 };
 
 }
 
 #endif // MediaQueryList_h