Don't squash layers with non-translation transforms.

third_party/WebKit/Source/core/layout/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 148 matching lines @@
 
     if (layer->scrollParent() && layer->hasCompositingDescendant())
         return SquashingDisallowedReasonScrollChildWithCompositedDescendants;
 
     if (layer->opacityAncestor() != squashingLayer.opacityAncestor())
         return SquashingDisallowedReasonOpacityAncestorMismatch;
 
     if (layer->transformAncestor() != squashingLayer.transformAncestor())
         return SquashingDisallowedReasonTransformAncestorMismatch;
 
+    if (layer->transform() && !layer->transform()->isIdentityOrTranslation())
+        return SquashingDisallowedReasonNonTranslationTransform;
+
     if (layer->renderingContextRoot() != squashingLayer.renderingContextRoot())
         return SquashingDisallowedReasonRenderingContextMismatch;
 
     if (layer->hasFilter() || layer->filterAncestor() != squashingLayer.filterAncestor())
         return SquashingDisallowedReasonFilterMismatch;
 
     if (layer->nearestFixedPositionLayer() != squashingLayer.nearestFixedPositionLayer())
         return SquashingDisallowedReasonNearestFixedPositionMismatch;
     ASSERT(layer->layoutObject()->style()->position() != FixedPosition);
 
@@ skipping 127 matching lines @@
 
     PaintLayerStackingNodeIterator iterator(*layer->stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
     while (PaintLayerStackingNode* curNode = iterator.next())
         assignLayersToBackingsInternal(curNode->layer(), squashingState, layersNeedingPaintInvalidation);
 
     if (squashingState.hasMostRecentMapping && &squashingState.mostRecentMapping->owningLayer() == layer)
         squashingState.haveAssignedBackingsToEntireSquashingLayerSubtree = true;
 }
 
 } // namespace blink