Move viewport actions into an ApplyScroll callback.

third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h

Index: third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h
diff --git a/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h b/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h
new file mode 100644
index 0000000000000000000000000000000000000000..979da5f521df84f1f768f5853a131385d7af9d38
--- /dev/null
+++ b/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h
@@ -0,0 +1,41 @@
+// Copyright 2016 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 ViewportScrollCallback_h
+#define ViewportScrollCallback_h
+
+#include "core/page/scrolling/ScrollStateCallback.h"
+#include "platform/heap/Handle.h"
+#include "platform/scroll/ScrollTypes.h"
+
+namespace blink {
+
+class Document;
+class FloatSize;
+class FrameHost;
+class Element;
+class ScrollableArea;
+class ScrollState;
+
+class ViewportScrollCallback : public ScrollStateCallback {
+public:
+    ViewportScrollCallback(Document&, FrameHost&);
+    ~ViewportScrollCallback();
+
+    void handleEvent(ScrollState*) override;
+
+    DECLARE_VIRTUAL_TRACE();
+
+private:
+    bool shouldScrollTopControls(const FloatSize&, ScrollGranularity) const;
+    ScrollableArea* getRootFrameViewport() const;
+
+    WeakMember<Document> m_document;
+    WeakMember<FrameHost> m_frameHost;
+
+};
+
+} // namespace blink
+
+#endif // ViewportScrollCallback_h