Fix paint property under-invalidation of CSS clip on resize

third_party/WebKit/Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1717 matching lines @@
     Element& element = toElement(*node());
     element.setNeedsResizeObserverUpdate();
   }
 
   if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
     if (shouldClipOverflow()) {
       // The overflow clip paint property depends on the border box rect through
       // overflowClipRect(). The border box rect's size equals the frame rect's
       // size so we trigger a paint property update when the frame rect changes.
       setNeedsPaintPropertyUpdate();
+    } else if (hasClip()) {

[chrishtr, 2017/02/28 00:11:18]

Is this needed for clip-path as well?

[Xianzhu, 2017/02/28 00:17:20]

We seem not to support clip-path in paint property tree for now. Should we?

[trchen, 2017/02/28 00:43:28]

Thanks for the heads up! Yea, I think this will be needed for clip-path as well,
and definitely is needed for masks. (Because masks implicitly create a clip,
which is implemented by clip node.)

I think it makes sense to match
LayoutBox::paintedOutputOfObjectHasNoEffectRegardlessOfSize().
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/layout/La...

+      // The used value of CSS clip may depend on size of the box, e.g. for
+      // clip: rect(auto auto auto -5px).
+      setNeedsPaintPropertyUpdate();
     } else if (styleRef().hasTransform() || styleRef().hasPerspective()) {
       // Relative lengths (e.g., percentage values) in transform, perspective,
       // transform-origin, and perspective-origin can depend on the size of the
       // frame rect, so force a property update if it changes.
       // TODO(pdr): We only need to update properties if there are relative
       // lengths.
       setNeedsPaintPropertyUpdate();
     }
   }
 }
@@ skipping 3982 matching lines @@
 
 void LayoutBox::MutableForPainting::
     savePreviousContentBoxSizeAndLayoutOverflowRect() {
   auto& rareData = layoutBox().ensureRareData();
   rareData.m_hasPreviousContentBoxSizeAndLayoutOverflowRect = true;
   rareData.m_previousContentBoxSize = layoutBox().contentBoxRect().size();
   rareData.m_previousLayoutOverflowRect = layoutBox().layoutOverflowRect();
 }
 
 }  // namespace blink