Disallow fragmentation of composited content.

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 165 matching lines @@
         return SquashingDisallowedReasonFilterMismatch;
 
     if (layer->nearestFixedPositionLayer() != squashingLayer.nearestFixedPositionLayer())
         return SquashingDisallowedReasonNearestFixedPositionMismatch;
     ASSERT(layer->layoutObject()->style()->position() != FixedPosition);
 
     if ((squashingLayer.layoutObject()->style()->subtreeWillChangeContents() && squashingLayer.layoutObject()->style()->isRunningAnimationOnCompositor())
         || squashingLayer.layoutObject()->style()->shouldCompositeForCurrentAnimations())
         return SquashingDisallowedReasonSquashingLayerIsAnimating;
 
+    if (layer->enclosingPaginationLayer())
+        return SquashingDisallowedReasonFragmentedContent;
+
     return SquashingDisallowedReasonsNone;
 }
 
 void CompositingLayerAssigner::updateSquashingAssignment(PaintLayer* layer, SquashingState& squashingState, const CompositingStateTransitionType compositedLayerUpdate,
     Vector<PaintLayer*>& 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 PaintLayer'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
     // when they have a composited negative z-index child, such layers will never need squashing so it is not yet an issue.
@@ skipping 113 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