Invalidate background-attachment:fixed on scroll.

third_party/WebKit/Source/core/layout/LayoutBox.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, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. 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 236 matching lines @@
                     scrollableArea->verticalScrollbar()->styleChanged();
             }
         }
     }
     updateShapeOutsideInfoAfterStyleChange(*style(), oldStyle);
     updateGridPositionAfterStyleChange(oldStyle);
 
     if (LayoutMultiColumnSpannerPlaceholder* placeholder = this->spannerPlaceholder())
         placeholder->layoutObjectInFlowThreadStyleDidChange(oldStyle);
 
-    updateSlowRepaintStatusAfterStyleChange();
+    updateBackgroundAttachmentFixedStatusAfterStyleChange();
 
     if (oldStyle) {
         LayoutFlowThread* flowThread = flowThreadContainingBlock();
         if (flowThread && flowThread != this)
             flowThread->flowThreadDescendantStyleDidChange(this, diff, *oldStyle);
     }
 }
 
-void LayoutBox::updateSlowRepaintStatusAfterStyleChange()
+void LayoutBox::updateBackgroundAttachmentFixedStatusAfterStyleChange()
 {
     if (!frameView())
         return;
 
     // On low-powered/mobile devices, preventing blitting on a scroll can cause noticeable delays
     // when scrolling a page with a fixed background image. As an optimization, assuming there are
     // no fixed positoned elements on the page, we can acclerate scrolling (via blitting) if we
     // ignore the CSS property "background-attachment: fixed".
     bool ignoreFixedBackgroundAttachment = RuntimeEnabledFeatures::fastMobileScrollingEnabled();
     if (ignoreFixedBackgroundAttachment)
         return;
 
     // An object needs to be repainted on frame scroll when it has background-attachment:fixed.
-    // LayoutObject is responsible for painting root background, thus the root element (and the
+    // LayoutView is responsible for painting root background, thus the root element (and the
     // body element if html element has no background) skips painting backgrounds.
-    bool isSlowRepaintObject = !isDocumentElement() && !backgroundStolenForBeingBody() && styleRef().hasFixedBackgroundImage();
+    bool isBackgroundAttachmentFixedObject = !isDocumentElement() && !backgroundStolenForBeingBody() && styleRef().hasFixedBackgroundImage();
     if (isLayoutView() && view()->compositor()->supportsFixedRootBackgroundCompositing()) {
         if (styleRef().hasEntirelyFixedBackground())
-            isSlowRepaintObject = false;
+            isBackgroundAttachmentFixedObject = false;
     }
 
-    setIsSlowRepaintObject(isSlowRepaintObject);
+    setIsBackgroundAttachmentFixedObject(isBackgroundAttachmentFixedObject);
 }
 
 void LayoutBox::updateShapeOutsideInfoAfterStyleChange(const ComputedStyle& style, const ComputedStyle* oldStyle)
 {
     const ShapeValue* shapeOutside = style.shapeOutside();
     const ShapeValue* oldShapeOutside = oldStyle ? oldStyle->shapeOutside() : ComputedStyle::initialShapeOutside();
 
     Length shapeMargin = style.shapeMargin();
     Length oldShapeMargin = oldStyle ? oldStyle->shapeMargin() : ComputedStyle::initialShapeMargin();
 
@@ skipping 4455 matching lines @@
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender(*this, style()->effectiveZoom()) && borderImage->isLoaded();
 }
 
 ShapeOutsideInfo* LayoutBox::shapeOutsideInfo() const
 {
     return ShapeOutsideInfo::isEnabledFor(*this) ? ShapeOutsideInfo::info(*this) : nullptr;
 }
 
 } // namespace blink