Generalize browser controls adjustment for arbitrary scrollers.

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/geometry/IntSize.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class Element;
 class FrameHost;
 class GraphicsLayer;
 class PaintLayer;
 class RootFrameViewport;
 class ScrollStateCallback;
@@ skipping 39 matching lines @@
   PaintLayer* rootScrollerPaintLayer() const;
 
   // Returns the Element that's the global root scroller.
   Element* globalRootScroller() const;
 
   // Called when the root scroller in any frames on the page has changed.
   void didChangeRootScroller();
 
   void mainFrameViewResized();
 
+  // Returns the ScrollableArea associated with the globalRootScroller(). Note,
+  // this isn't necessarily the PLSA belonging to the root scroller Element's
+  // LayoutBox.  If the root scroller is the documentElement then we use the
+  // FrameView (or LayoutView if root-layer-scrolls).
+  ScrollableArea* rootScrollerArea() const;
+
+  // Returns the size we should use for the root scroller, accounting for top
+  // controls adjustment and using the root FrameView.
+  IntSize rootScrollerVisibleArea() const;
+
  private:
   TopDocumentRootScrollerController(FrameHost&);
 
   // Calculates the Element that should be the globalRootScroller. On a
   // simple page, this will simply the root frame's effectiveRootScroller but
   // if the root scroller is set to an iframe, this will then descend into
   // the iframe to find its effective root scroller.
   Element* findGlobalRootScrollerElement();
 
   // Should be called to ensure the correct element is currently set as the
@@ skipping 15 matching lines @@
   // m_viewportApplyScroll has been created, it will always be set on this
   // Element.
   WeakMember<Element> m_globalRootScroller;
 
   WeakMember<FrameHost> m_frameHost;
 };
 
 }  // namespace blink
 
 #endif  // RootScrollerController_h