Include control clip in list of clip-related properties.

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 115 matching lines @@
     return SquashingDisallowedReasonWouldBreakPaintOrder;
 
   DCHECK(squashingState.hasMostRecentMapping);
   const PaintLayer& squashingLayer =
       squashingState.mostRecentMapping->owningLayer();
 
   // FIXME: this special case for video exists only to deal with corner cases
   // where a LayoutVideo does not report that it needs to be directly
   // composited.  Video does not currently support sharing a backing, but this
   // could be generalized in the future. The following layout tests fail if we
-  // permit the video to share a backing with other layers.
+  // permit the video to share a backing with other laycers.

[amineer, 2017/03/23 17:30:12]

typo?

   //
   // compositing/video/video-controls-layer-creation.html
   if (layer->layoutObject().isVideo() ||
       squashingLayer.layoutObject().isVideo())
     return SquashingDisallowedReasonSquashingVideoIsDisallowed;
 
   // Don't squash iframes, frames or plugins.
   // FIXME: this is only necessary because there is frame code that assumes that
   // composited frames are not squashed.
   if (layer->layoutObject().isLayoutPart() ||
@@ skipping 19 matching lines @@
   // has no CLM nor a child containment graphics layer).
   if (m_compositor->clipsCompositingDescendants(layer))
     return SquashingDisallowedReasonSquashedLayerClipsCompositingDescendants;
 
   if (layer->scrollsWithRespectTo(&squashingLayer))
     return SquashingDisallowedReasonScrollsWithRespectToSquashingLayer;
 
   if (layer->scrollParent() && layer->hasCompositingDescendant())
     return SquashingDisallowedReasonScrollChildWithCompositedDescendants;
 
+  // It's possible for this reason to be true but not the above ones. One
+  // example is scrolling input boxes, which do not "scroll" but use
+  // scrolling contents layers to allow typing beyond the input bounds.
+  if ((squashingLayer.getScrollableArea() &&
+       squashingLayer.getScrollableArea()->usesCompositedScrolling()) ||
+      (layer->getScrollableArea() &&
+       layer->getScrollableArea()->usesCompositedScrolling()))
+    return SquashingDisallowedReasonCompositedScrolling;
+
   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())
@@ skipping 164 matching lines @@
   while (PaintLayerStackingNode* curNode = iterator.next())
     assignLayersToBackingsInternal(curNode->layer(), squashingState,
                                    layersNeedingPaintInvalidation);
 
   if (squashingState.hasMostRecentMapping &&
       &squashingState.mostRecentMapping->owningLayer() == layer)
     squashingState.haveAssignedBackingsToEntireSquashingLayerSubtree = true;
 }
 
 }  // namespace blink