Ensure that we consistently check contains: paint for fixed position containment.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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
@@ skipping 985 matching lines @@
 {
     ASSERT(ancestorToStopAt != this);
 
     bool ancestorSkipped;
     LayoutObject* container = this->container(ancestorToStopAt, &ancestorSkipped);
     if (!container)
         return nullptr;
 
     bool isInline = isLayoutInline();
     bool isFixedPos = !isInline && style()->position() == FixedPosition;
-    bool hasTransform = !isInline && hasLayer() && layer()->transform();
+    bool containsFixedPosition = canContainFixedPositionObjects();
 
     LayoutSize adjustmentForSkippedAncestor;
     if (ancestorSkipped) {
         // There can't be a transform between paintInvalidationContainer and ancestorToStopAt, because transforms create containers, so it should be safe
         // to just subtract the delta between the ancestor and ancestorToStopAt.
         adjustmentForSkippedAncestor = -ancestorToStopAt->offsetFromAncestorContainer(container);
     }
 
     LayoutSize containerOffset = offsetFromContainer(container);
     bool offsetDependsOnPoint;
     if (isLayoutFlowThread()) {
         containerOffset += columnOffset(LayoutPoint());
         offsetDependsOnPoint = true;
     } else {
         offsetDependsOnPoint = container->style()->isFlippedBlocksWritingMode() && container->isBox();
     }
 
     bool preserve3D = container->style()->preserves3D() || style()->preserves3D();
     GeometryInfoFlags flags = 0;
     if (preserve3D)
         flags |= AccumulatingTransform;
     if (offsetDependsOnPoint)
         flags |= IsNonUniform;
     if (isFixedPos)
         flags |= IsFixedPosition;
-    if (hasTransform)
-        flags |= HasTransform;
+    if (containsFixedPosition)
+        flags |= ContainsFixedPosition;
     if (shouldUseTransformFromContainer(container)) {
         TransformationMatrix t;
         getTransformFromContainer(container, containerOffset, t);
         t.translateRight(adjustmentForSkippedAncestor.width().toFloat(), adjustmentForSkippedAncestor.height().toFloat());
         geometryMap.push(this, t, flags, LayoutSize());
     } else {
         containerOffset += adjustmentForSkippedAncestor;
         geometryMap.push(this, containerOffset, flags, LayoutSize());
     }
 
@@ skipping 69 matching lines @@
     if (rootElementStyle->hasBackground())
         return false;
 
     if (node() != document().firstBodyElement())
         return false;
 
     return true;
 }
 
 } // namespace blink