Fix LayoutObject::mapLocalToAncestor() for fixed under absolute

third_party/WebKit/Source/core/layout/LayoutView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc.
  *               All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 382 matching lines @@
   } else {
     geometryMap.push(this, offset, 0, offsetForFixedPosition);
   }
 
   return container;
 }
 
 void LayoutView::mapAncestorToLocal(const LayoutBoxModelObject* ancestor,
                                     TransformState& transformState,
                                     MapCoordinatesFlags mode) const {
-  if (this == ancestor)
-    return;
-
-  if (mode & TraverseDocumentBoundaries) {
+  if (this != ancestor && (mode & TraverseDocumentBoundaries)) {
     if (LayoutPart* parentDocLayoutObject = toLayoutPart(
             LayoutAPIShim::layoutObjectFrom(frame()->ownerLayoutItem()))) {
       // A LayoutView is a containing block for fixed-position elements, so
       // don't carry this state across frames.
       parentDocLayoutObject->mapAncestorToLocal(ancestor, transformState,
                                                 mode & ~IsFixed);
 
       transformState.move(parentDocLayoutObject->contentBoxOffset());
       transformState.move(LayoutSize(-frame()->view()->scrollOffset()));
     }
   } else {
-    ASSERT(!ancestor);
+    DCHECK(this == ancestor || !ancestor);
   }
 
   if (mode & IsFixed)
     transformState.move(LayoutSize(frame()->view()->scrollOffset()));
 }
 
 void LayoutView::computeSelfHitTestRects(Vector<LayoutRect>& rects,
                                          const LayoutPoint&) const {
   // Record the entire size of the contents of the frame. Note that we don't
   // just use the viewport size (containing block) here because we want to
@@ skipping 633 matching lines @@
   if (block)
     block->adjustChildDebugRect(rect);
 
   rect.setWidth(LayoutUnit(viewWidth(IncludeScrollbars)));
   rect.setHeight(LayoutUnit(viewHeight(IncludeScrollbars)));
 
   return rect;
 }
 
 }  // namespace blink