Have srcset respond to viewport changes

Source/core/frame/ViewportChangeNotifier.h

Index: Source/core/frame/ViewportChangeNotifier.h
diff --git a/Source/core/frame/ViewportChangeNotifier.h b/Source/core/frame/ViewportChangeNotifier.h
new file mode 100644
index 0000000000000000000000000000000000000000..f8fc8659c793373ddff641359340f4bcd88d6e9c
--- /dev/null
+++ b/Source/core/frame/ViewportChangeNotifier.h
@@ -0,0 +1,35 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ViewportChangeNotifier_h
+#define ViewportChangeNotifier_h
+
+#include "platform/heap/Handle.h"
+
+namespace WebCore {
+
+class ViewportChangeListener : public RefCountedWillBeGarbageCollected<ViewportChangeListener> {
+public:
+    virtual void viewportChanged() = 0;
+    virtual ~ViewportChangeListener() { }

[haraken, 2014/07/11 06:10:21]

You'll need to use
DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(ViewportChangeListener) in the
header file and use
DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(ViewportChangeListener).

+};
+
+class ViewportChangeNotifier {

[haraken, 2014/07/11 06:10:21]

This should be:

class ViewportChangeNotifier : public
NoBaseWillBeGarbageCollected<ViewportChangeNotifier> { ... };

+public:
+    static PassOwnPtrWillBeRawPtr<ViewportChangeNotifier> create();
+    void addListener(PassRefPtrWillBeRawPtr<ViewportChangeListener>);
+    void removeListener(PassRefPtrWillBeRawPtr<ViewportChangeListener>);
+    void viewportChanged();
+
+    typedef WillBeHeapHashSet<RefPtrWillBeMember<ViewportChangeListener> > ListenerContainer;
+
+private:
+    ViewportChangeNotifier() { };
+
+    ListenerContainer m_listeners;

[haraken, 2014/07/11 06:10:21]

You need to add a trace() method and trace m_listeners.

+};
+
+} // namespace
+
+#endif // MediaQueryBlockWatcher_h