Invalidate background-attachment:fixed on scroll.

third_party/WebKit/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 3412 matching lines @@
         {
             object.setShouldDoFullPaintInvalidation();
         }
     };
 
     // Need to access the current compositing status.
     DisableCompositingQueryAsserts disabler;
     traverseNonCompositingDescendants(*this, Functor());
 }
 
 void LayoutObject::setIsSlowRepaintObject(bool isSlowRepaintObject)

[Xianzhu, 2015/10/12 16:05:51]

Can you also rename this function and
LayoutBox::updateSlowRepaintStatusAfterStyleChange()?

 {
     ASSERT(frameView());
     if (m_bitfields.isSlowRepaintObject() == isSlowRepaintObject)
         return;
     m_bitfields.setIsSlowRepaintObject(isSlowRepaintObject);
     if (isSlowRepaintObject)
-        frameView()->addSlowRepaintObject();
+        frameView()->addBackgroundAttachmentFixedObject(this);
     else
-        frameView()->removeSlowRepaintObject();
+        frameView()->removeBackgroundAttachmentFixedObject(this);
 }
 
 } // namespace blink
 
 #ifndef NDEBUG
 
 void showTree(const blink::LayoutObject* object)
 {
     if (object)
         object->showTreeForThis();
@@ skipping 20 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif