Cleanup and refactor RootScrollerController.

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

-// 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 RootViewportScrollCallback_h
-#define RootViewportScrollCallback_h
-
-#include "core/page/scrolling/ViewportScrollCallback.h"
-#include "platform/heap/Handle.h"
-#include "platform/scroll/ScrollTypes.h"
-
-namespace blink {
-
-class FloatSize;
-class ScrollableArea;
-class ScrollState;
-class TopControls;
-class OverscrollController;
-class RootFrameViewport;
-
-// The ViewportScrollCallback used by the one root frame on the page. This
-// callback provides scrolling of the frame as well as associated actions like
-// top controls movement and overscroll glow.
-class RootViewportScrollCallback : public ViewportScrollCallback {
-public:
-    // The TopControls and OverscrollController are given to the
-    // RootViewportScrollCallback but are not owned or kept alive by it.
-    static RootViewportScrollCallback* create(
-        TopControls* topControls,
-        OverscrollController* overscrollController,
-        RootFrameViewport& rootFrameViewport)
-    {
-        return new RootViewportScrollCallback(
-            topControls, overscrollController, rootFrameViewport);
-    }
-
-    virtual ~RootViewportScrollCallback();
-
-    void handleEvent(ScrollState*) override;
-    void setScroller(ScrollableArea*) override;
-
-    DECLARE_VIRTUAL_TRACE();
-
-private:
-    // RootViewportScrollCallback does not assume ownership of TopControls or of
-    // OverscrollController.
-    RootViewportScrollCallback(TopControls*, OverscrollController*, RootFrameViewport&);
-
-    bool shouldScrollTopControls(const FloatSize&, ScrollGranularity) const;
-    bool scrollTopControls(ScrollState&);
-
-    WeakMember<TopControls> m_topControls;
-    WeakMember<OverscrollController> m_overscrollController;
-    WeakMember<RootFrameViewport> m_rootFrameViewport;
-};
-
-} // namespace blink
-
-#endif // RootViewportScrollCallback_h