Don't squash layers that have filters.

Source/core/rendering/compositing/CompositingLayerAssigner.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 147 matching lines @@
 
     const RenderLayer::AncestorDependentCompositingInputs& compositingInputs = layer->ancestorDependentCompositingInputs();
     const RenderLayer::AncestorDependentCompositingInputs& squashingLayerCompositingInputs = squashingLayer.ancestorDependentCompositingInputs();
 
     if (compositingInputs.opacityAncestor != squashingLayerCompositingInputs.opacityAncestor)
         return CompositingReasonSquashingOpacityAncestorMismatch;
 
     if (compositingInputs.transformAncestor != squashingLayerCompositingInputs.transformAncestor)
         return CompositingReasonSquashingTransformAncestorMismatch;
 
-    if (compositingInputs.filterAncestor != squashingLayerCompositingInputs.filterAncestor)
-        return CompositingReasonSquashingFilterAncestorMismatch;
+    if (layer->hasFilter() || compositingInputs.filterAncestor != squashingLayerCompositingInputs.filterAncestor)
+        return CompositingReasonSquashingFilterMismatch;
 
     return CompositingReasonNone;
 }
 
 void CompositingLayerAssigner::updateSquashingAssignment(RenderLayer* layer, SquashingState& squashingState, const CompositingStateTransitionType compositedLayerUpdate,
     Vector<RenderLayer*>& layersNeedingPaintInvalidation)
 {
     // NOTE: In the future as we generalize this, the background of this layer may need to be assigned to a different backing than
     // the squashed RenderLayer's own primary contents. This would happen when we have a composited negative z-index element that needs
     // to paint on top of the background, but below the layer's main contents. For now, because we always composite layers
@@ skipping 102 matching lines @@
 
     RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
     while (RenderLayerStackingNode* curNode = iterator.next())
         assignLayersToBackingsInternal(curNode->layer(), squashingState, layersNeedingPaintInvalidation);
 
     if (squashingState.hasMostRecentMapping && &squashingState.mostRecentMapping->owningLayer() == layer)
         squashingState.haveAssignedBackingsToEntireSquashingLayerSubtree = true;
 }
 
 }