Move TopDocumentRootScrollerController to a separate object on FrameHost

third_party/WebKit/Source/core/page/scrolling/RootScrollerController.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 RootScrollerController_h
 #define RootScrollerController_h
 
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 
@@ skipping 10 matching lines @@
 // scroller causes top controls movement, overscroll effects and prevents
 // chaining scrolls up further in the DOM. It can be set from script using
 // document.setRootScroller.
 //
 // There are two notions of a root scroller in this class: m_rootScroller and
 // m_effectiveRootScroller. The former is the Element that was set as the root
 // scroller using document.setRootScroller. If the page didn't set a root
 // scroller this will be nullptr. The "effective" root scroller is the current
 // element we're using internally to apply viewport scrolling actions.  The
 // effective root scroller will only be null during document initialization.
-// Both these elements are from this controller's associated Document. The final
-// "global" root scroller, the one whose scrolling hides top controls, may be in
-// a different frame.
+// Both these elements come from this controller's associated Document. The
+// final "global" root scroller, the one whose scrolling hides top controls,
+// may be in a different frame.
 //
 // If the currently set m_rootScroller is a valid element to become the root
 // scroller, it will be promoted to the effective root scroller. If it is not
 // valid, the effective root scroller will fall back to a default Element (see
 // defaultEffectiveRootScroller()). The rules for what makes an element a valid
 // root scroller are set in isValidRootScroller(). The validity of the current
 // root scroller is re-checked after each layout.
 class CORE_EXPORT RootScrollerController
     : public GarbageCollected<RootScrollerController> {
 public:
-    // Creates a RootScrollerController for the given document. Note, instances
-    // of this class need to be made aware of lifecycle events, see the
-    // didUpdateLayout, didUpdateCompositing, etc. type methods below.
+    // Creates a RootScrollerController for the given document. Note: instances
+    // of this class need to be made aware of layout updates.
     static RootScrollerController* create(Document&);
 
-    DECLARE_VIRTUAL_TRACE();
+    DECLARE_TRACE();
 
     // Sets the element that will be used as the root scroller. This can be
     // nullptr, in which case we'll use the default element (documentElement) as
     // the effective root scroller.
     void set(Element*);
 
     // Returns the element currently set as the root scroller from script. This
     // differs from the effective root scroller since the set Element may not
     // currently be a valid root scroller. e.g. If the page sets an Element
     // with `display: none`, get() will return that element, even though the
     // effective root scroller will remain the element returned by
     // defaultEffectiveRootScroller().
     Element* get() const;
 
     // This returns the Element that's actually being used to control viewport
     // actions right now. This is different from get() if a root scroller hasn't
     // been set, or if the set root scroller isn't currently a valid scroller.
     Element* effectiveRootScroller() const;
 
     // This class needs to be informed of changes in layout so that it can
     // determine if the current root scroller is still valid or if it must be
     // replaced by the defualt root scroller.
     void didUpdateLayout();
 
-    // This class needs to be informed of changes to compositing so that it can
-    // update the compositor when the effective root scroller changes.
-    virtual void didUpdateCompositing();
-
-    // This class needs to be informed when the document has been attached to a
-    // FrameView so that we can initialize the viewport scroll callback.
-    virtual void didAttachDocument();
-
-    // Returns the GraphicsLayer for the current effective root scroller
-    // element.
-    virtual GraphicsLayer* rootScrollerLayer();
-
-    // 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.
-    virtual bool isViewportScrollCallback(const ScrollStateCallback*) const;
-
+    // Returns the PaintLayer associated with the currently effective root
+    // scroller.
     PaintLayer* rootScrollerPaintLayer() const;
 
-protected:
+private:
     RootScrollerController(Document&);
 
-    // Called when the root scroller of any descendant frames changes. This
-    // will only ever be called on the top document's RootScrollerController.
-    virtual void globalRootScrollerMayHaveChanged();
-
-    // Returns the ScrollableArea to use to scroll the given Element.
-    ScrollableArea* scrollableAreaFor(const Element&) const;
-
-    // The owning Document whose root scroller this object manages.
-    WeakMember<Document> m_document;
-
-private:
     // Ensures the effective root scroller is currently valid and replaces it
     // with the default if not.
     void recomputeEffectiveRootScroller();
 
     // Determines whether the given element meets the criteria to become the
     // effective root scroller.
     bool isValidRootScroller(const Element&) const;
 
     // Returns the Element that should be used if the currently set
     // m_rootScroller isn't valid to be a root scroller.
     Element* defaultEffectiveRootScroller();
 
+    // The owning Document whose root scroller this object manages.
+    WeakMember<Document> m_document;
+
     // The Element that was set from script as rootScroller for this Document.
     // Depending on its validity to be the root scroller (e.g. a display: none
     // element isn't a valid root scroller), this may not actually be the
     // Element being used as the root scroller.
     WeakMember<Element> m_rootScroller;
 
     // The element currently being used as the root scroller in this Document.
     // If the m_rootScroller is valid this will point to it. Otherwise, it'll
     // use a default Element.
     WeakMember<Element> m_effectiveRootScroller;
 };
 
 } // namespace blink
 
 #endif // RootScrollerController_h