Revert of Split RootScrollerController into top-document and child-document classes

third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.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 TopDocumentRootScrollerController_h
-#define TopDocumentRootScrollerController_h
-
-#include "core/CoreExport.h"
-#include "core/page/scrolling/RootScrollerController.h"
-#include "platform/heap/Handle.h"
-
-namespace blink {
-
-class Document;
-class Element;
-class GraphicsLayer;
-class ScrollStateCallback;
-class ViewportScrollCallback;
-
-// The RootScrollerController used to manage the root scroller for the top
-// level Document on a page. In addition to the regular RootScroller duties
-// such as keeping track of which Element is set as root scroller and which is
-// the effective root scroller, this class is also responsible for setting the
-// ViewportApplyScroll on the one Element on a page that should apply viewport
-// scrolling actions.
-class CORE_EXPORT TopDocumentRootScrollerController
-    : public RootScrollerController {
-public:
-    static TopDocumentRootScrollerController* create(Document&);
-
-    DECLARE_VIRTUAL_TRACE();
-
-    // This class needs to be informed of changes to compositing so that it can
-    // update the compositor when the effective root scroller changes.
-    void didUpdateCompositing() override;
-
-    // This class needs to be informed when the document has been attached to a
-    // FrameView so that we can initialize the viewport scroll callback.
-    void didAttachDocument() override;
-
-    // Returns true if the given ScrollStateCallback is the ViewportScrollCallback managed
-    // by this class.
-    // TODO(bokan): Temporarily needed to allow ScrollCustomization to
-    // differentiate between real custom callback and the built-in viewport
-    // apply scroll. crbug.com/623079.
-    bool isViewportScrollCallback(
-        const ScrollStateCallback*) const override;
-
-protected:
-    TopDocumentRootScrollerController(Document&);
-
-    // Ensures the effective root scroller is currently valid and replaces it
-    // with the default if not.
-    void updateEffectiveRootScroller() override;
-
-private:
-    // Ensures that the element that should be used as the root scroller on the
-    // page has the m_viewportApplyScroll callback set on it.
-    void setViewportApplyScrollOnRootScroller();
-
-    // The apply-scroll callback that moves top controls and produces
-    // overscroll effects. This class makes sure this callback is set on the
-    // appropriate root scroller element.
-    Member<ViewportScrollCallback> m_viewportApplyScroll;
-
-    // Tracks which element currently has the m_viewportApplyScroll set to it.
-    WeakMember<Element> m_currentViewportApplyScrollHost;
-};
-
-} // namespace blink
-
-#endif // RootScrollerController_h