Parent stacking context of a backdrop filter should isolate itself

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

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 410 matching lines @@
             reasonsToComposite |= layer->potentialCompositingReasonsFromStyle() & CompositingReasonInlineTransform;
 
         // If the original layer is composited, the reflection needs to be, too.
         if (layer->reflectionInfo()) {
             // FIXME: Shouldn't we call computeCompositingRequirements to handle a reflection overlapping with another layoutObject?
             PaintLayer* reflectionLayer = layer->reflectionInfo()->reflectionLayer();
             CompositingReasons reflectionCompositingReason = willBeCompositedOrSquashed ? CompositingReasonReflectionOfCompositedParent : CompositingReasonNone;
             reflectionLayer->setCompositingReasons(reflectionCompositingReason, CompositingReasonReflectionOfCompositedParent);
         }
 
-        if (willBeCompositedOrSquashed && layer->layoutObject()->style()->hasBlendMode())
+        if (willBeCompositedOrSquashed && (layer->layoutObject()->style()->hasBlendMode() || layer->layoutObject()->style()->hasBackdropFilter()))

[pdr., 2016/09/29 21:54:49]

Since webkit has the only shipping implementation of backdrop filter, I think it
makes sense to fix them too. Can you file a bug in bugs.webkit.org?

[trchen, 2016/09/29 22:23:33]

Sure! I'm doing now.

             currentRecursionData.m_hasUnisolatedCompositedBlendingDescendant = true;
 
         // Tell the parent it has compositing descendants.
         if (willBeCompositedOrSquashed)
             currentRecursionData.m_subtreeIsCompositing = true;
 
         // Turn overlap testing off for later layers if it's already off, or if we have an animating transform.
         // Note that if the layer clips its descendants, there's no reason to propagate the child animation to the parent layers. That's because
         // we know for sure the animation is contained inside the clipping rectangle, which is already added to the overlap map.
         bool isCompositedClippingLayer = canBeComposited && (reasonsToComposite & CompositingReasonClipsCompositingDescendants);
         bool isCompositedWithInlineTransform = reasonsToComposite & CompositingReasonInlineTransform;
         if ((!childRecursionData.m_testingOverlap && !isCompositedClippingLayer) || layer->layoutObject()->style()->hasCurrentTransformAnimation() || isCompositedWithInlineTransform)
             currentRecursionData.m_testingOverlap = false;
 
         if (childRecursionData.m_compositingAncestor == layer)
             overlapMap.finishCurrentOverlapTestingContext();
 
         descendantHas3DTransform |= anyDescendantHas3DTransform || layer->has3DTransform();
     }
 
     // At this point we have finished collecting all reasons to composite this layer.
     layer->setCompositingReasons(reasonsToComposite);
 }
 
 } // namespace blink