CompositingInputsUpdater should do more clip parent analysis

third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/compositing/CompositingInputsUpdater.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
@@ skipping 134 matching lines @@
             rareProperties.opacityAncestor = parent->isTransparent() ? parent : parent->opacityAncestor();
             rareProperties.transformAncestor = parent->transform() ? parent : parent->transformAncestor();
             rareProperties.filterAncestor = parent->hasFilterInducingProperty() ? parent : parent->filterAncestor();
             bool layerIsFixedPosition = layer->layoutObject()->style()->position() == FixedPosition;
             rareProperties.nearestFixedPositionLayer = layerIsFixedPosition ? layer : parent->nearestFixedPositionLayer();
 
             if (info.hasAncestorWithClipRelatedProperty) {
                 const PaintLayer* parentLayerOnClippingContainerChain = findParentLayerOnClippingContainerChain(layer);
                 const bool parentHasClipRelatedProperty = parentLayerOnClippingContainerChain->layoutObject()->hasClipRelatedProperty();
                 properties.clippingContainer = parentHasClipRelatedProperty ? parentLayerOnClippingContainerChain->layoutObject() : parentLayerOnClippingContainerChain->clippingContainer();
+
+                if (layer->layoutObject()->isOutOfFlowPositioned() && !layer->subtreeIsInvisible()) {
+                    const PaintLayer* clippingLayer = properties.clippingContainer ? properties.clippingContainer->enclosingLayer() : layer->compositor()->rootLayer();
+                    if (hasClippedStackingAncestor(layer, clippingLayer))
+                        rareProperties.clipParent = clippingLayer;
+                }
             }
 
             if (info.lastScrollingAncestor) {
                 const LayoutObject* containingBlock = layer->layoutObject()->containingBlock();
                 const PaintLayer* parentLayerOnContainingBlockChain = findParentLayerOnContainingBlockChain(containingBlock);
 
                 rareProperties.ancestorScrollingLayer = parentLayerOnContainingBlockChain->ancestorScrollingLayer();
                 if (parentLayerOnContainingBlockChain->scrollsOverflow())
                     rareProperties.ancestorScrollingLayer = parentLayerOnContainingBlockChain;
 
-                if (layer->layoutObject()->isOutOfFlowPositioned() && !layer->subtreeIsInvisible()) {
-                    const PaintLayer* clippingLayer = properties.clippingContainer ? properties.clippingContainer->enclosingLayer() : layer->compositor()->rootLayer();
-                    if (hasClippedStackingAncestor(layer, clippingLayer))
-                        rareProperties.clipParent = clippingLayer;
-                }
-
                 if (layer->stackingNode()->isStacked()
                     && rareProperties.ancestorScrollingLayer
                     && !info.ancestorStackingContext->layoutObject()->isDescendantOf(rareProperties.ancestorScrollingLayer->layoutObject()))
                     rareProperties.scrollParent = rareProperties.ancestorScrollingLayer;
             }
         }
 
         layer->updateAncestorDependentCompositingInputs(properties, rareProperties, info.hasAncestorWithClipPath);
     }
 
@@ skipping 34 matching lines @@
     ASSERT(!layer->childNeedsCompositingInputsUpdate());
     ASSERT(!layer->needsCompositingInputsUpdate());
 
     for (PaintLayer* child = layer->firstChild(); child; child = child->nextSibling())
         assertNeedsCompositingInputsUpdateBitsCleared(child);
 }
 
 #endif
 
 } // namespace blink