Revert of Fix slow repaint object registration

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 1818 matching lines @@
         if (LayoutBlock* container = containingBlock())
             container->setNeedsOverflowRecalcAfterStyleChange();
     }
 
     if (updatedDiff.needsPaintInvalidationLayer())
         setShouldDoFullPaintInvalidationIncludingNonCompositingDescendants();
     else if (diff.needsPaintInvalidationObject() || updatedDiff.needsPaintInvalidationObject())
         setShouldDoFullPaintInvalidation();
 }
 
+static inline bool layoutObjectHasBackground(const LayoutObject* layoutObject)
+{
+    return layoutObject && layoutObject->hasBackground();
+}
+
 void LayoutObject::styleWillChange(StyleDifference diff, const ComputedStyle& newStyle)
 {
     if (m_style) {
         // If our z-index changes value or our visibility changes,
         // we need to dirty our stacking context's z-order list.
         bool visibilityChanged = m_style->visibility() != newStyle.visibility()
             || m_style->zIndex() != newStyle.zIndex()
             || m_style->hasAutoZIndex() != newStyle.hasAutoZIndex();
         if (visibilityChanged) {
             document().setAnnotatedRegionsDirty(true);
@@ skipping 25 matching lines @@
         // Clearing these bits is required to avoid leaving stale layoutObjects.
         // FIXME: We shouldn't need that hack if our logic was totally correct.
         if (diff.needsLayout()) {
             setFloating(false);
             clearPositionedState();
         }
     } else {
         s_affectsParentBlock = false;
     }
 
+    if (view()->frameView()) {
+        bool shouldBlitOnFixedBackgroundImage = false;
+        if (RuntimeEnabledFeatures::fastMobileScrollingEnabled()) {
+            // 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".
+            shouldBlitOnFixedBackgroundImage = true;
+        }
+        bool newStyleSlowScroll = !shouldBlitOnFixedBackgroundImage && newStyle.hasFixedBackgroundImage();
+        bool oldStyleSlowScroll = m_style && !shouldBlitOnFixedBackgroundImage && m_style->hasFixedBackgroundImage();
+
+        bool drawsRootBackground = isDocumentElement() || (isBody() && !layoutObjectHasBackground(document().documentElement()->layoutObject()));
+        if (drawsRootBackground && !shouldBlitOnFixedBackgroundImage) {
+            if (view()->compositor()->supportsFixedRootBackgroundCompositing()) {
+                if (newStyleSlowScroll && newStyle.hasEntirelyFixedBackground())
+                    newStyleSlowScroll = false;
+
+                if (oldStyleSlowScroll && m_style->hasEntirelyFixedBackground())
+                    oldStyleSlowScroll = false;
+            }
+        }
+
+        if (oldStyleSlowScroll != newStyleSlowScroll) {
+            if (oldStyleSlowScroll)
+                view()->frameView()->removeSlowRepaintObject();
+            if (newStyleSlowScroll)
+                view()->frameView()->addSlowRepaintObject();
+        }
+    }
+
     // Elements with non-auto touch-action will send a SetTouchAction message
     // on touchstart in EventHandler::handleTouchEvent, and so effectively have
     // a touchstart handler that must be reported.
     //
     // Since a CSS property cannot be applied directly to a text node, a
     // handler will have already been added for its parent so ignore it.
     TouchAction oldTouchAction = m_style ? m_style->touchAction() : TouchActionAuto;
     if (node() && !node()->isTextNode() && (oldTouchAction == TouchActionAuto) != (newStyle.touchAction() == TouchActionAuto)) {
         EventHandlerRegistry& registry = document().frameHost()->eventHandlerRegistry();
         if (newStyle.touchAction() != TouchActionAuto)
@@ skipping 536 matching lines @@
 
         if (StyleImage* borderImage = m_style->borderImage().image())
             borderImage->removeClient(this);
 
         if (StyleImage* maskBoxImage = m_style->maskBoxImage().image())
             maskBoxImage->removeClient(this);
 
         removeShapeImageClient(m_style->shapeOutside());
     }
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->removeLayoutObject(this);
-
-    if (frameView())
-        setIsSlowRepaintObject(false);
 }
 
 void LayoutObject::insertedIntoTree()
 {
     // FIXME: We should ASSERT(isRooted()) here but generated content makes some out-of-order insertion.
 
     // Keep our layer hierarchy updated. Optimize for the common case where we don't have any children
     // and don't have a layer attached to ourselves.
     DeprecatedPaintLayer* layer = nullptr;
     if (slowFirstChild() || hasLayer()) {
@@ skipping 777 matching lines @@
 }
 
 // FIXME: If we had a flag to force invalidations in a whole subtree, we could get rid of this function (crbug.com/410097).
 void LayoutObject::setShouldDoFullPaintInvalidationIncludingNonCompositingDescendants()
 {
     // Need to access the current compositing status.
     DisableCompositingQueryAsserts disabler;
     setShouldDoFullPaintInvalidationIncludingNonCompositingDescendantsInternal(this);
 }
 
-void LayoutObject::setIsSlowRepaintObject(bool isSlowRepaintObject)
-{
-    ASSERT(frameView());
-    if (m_bitfields.isSlowRepaintObject() == isSlowRepaintObject)
-        return;
-    m_bitfields.setIsSlowRepaintObject(isSlowRepaintObject);
-    if (isSlowRepaintObject)
-        frameView()->addSlowRepaintObject();
-    else
-        frameView()->removeSlowRepaintObject();
-}
-
 } // namespace blink
 
 #ifndef NDEBUG
 
 void showTree(const blink::LayoutObject* object)
 {
     if (object)
         object->showTreeForThis();
     else
         fprintf(stderr, "Cannot showTree. Root is (nil)\n");
@@ skipping 18 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