Need to invalidate scrollbars in case they get repositioned.

Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 618 matching lines @@
 bool LayoutObject::skipInvalidationWhenLaidOutChildren() const
 {
     if (!neededLayoutBecauseOfChildren())
         return false;
 
     // SVG renderers need to be invalidated when their children are laid out.
     // RenderBlocks with line boxes are responsible to invalidate them so we can't ignore them.
     if (isSVG() || (isRenderBlockFlow() && toRenderBlockFlow(this)->firstLineBox()))
         return false;
 
-    return rendererHasNoBoxEffect();
+    return rendererHasNoBoxEffect() && !hasNonCompositedScrollbars();

[dsinclair, 2015/02/23 15:13:53]

Can we pull this out to be (assuming the following logic is still valid):

// some comment as to why this is special ....
if (hasNonCompositedScrolbars())
  return false;

return rendererHasNoBoxEffect();

[mstensho (USE GERRIT), 2015/02/23 17:22:38]

Done.

 }
 
 RenderBlock* LayoutObject::firstLineBlock() const
 {
     return 0;
 }
 
 static inline bool objectIsRelayoutBoundary(const LayoutObject* object)
 {
     // FIXME: In future it may be possible to broaden these conditions in order to improve performance.
@@ skipping 2534 matching lines @@
 {
     if (object1) {
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showRenderTreeAndMark(object1, "*", object2, "-", 0);
     }
 }
 
 #endif