Expand PaintLayer clip to account for hidden URL bar with document.rootScroller

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 499 matching lines @@
 
   FrameHost* host = layoutBox()->document().frameHost();
   DCHECK(host);
   TopDocumentRootScrollerController& controller =
       host->globalRootScrollerController();
 
   // The global root scroller should be clipped by the top FrameView rather
   // than it's overflow clipping box. This is to ensure that content exposed by
   // hiding the URL bar at the bottom of the screen is visible.
   if (this == controller.rootScrollerArea())
-    visibleSize = controller.rootScrollerVisibleArea();
+    visibleSize = controller.visibleContentRect(ExcludeScrollbars).size();
 
   // TODO(skobes): We should really ASSERT that contentSize >= visibleSize
   // when we are not the root layer, but we can't because contentSize is
   // based on stale layout overflow data (http://crbug.com/576933).
   contentSize = contentSize.expandedTo(visibleSize);
 
   return toIntSize(-scrollOrigin() + (contentSize - visibleSize));
 }
 
 IntRect PaintLayerScrollableArea::visibleContentRect(
@@ skipping 1574 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetAfterOverflowChange();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink