Tracking filter mutation via SVGElementProxy

third_party/WebKit/Source/core/css/resolver/MatchedPropertiesCache.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc.
  * All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
@@ skipping 118 matching lines @@
   if (style.getWritingMode() != ComputedStyle::initialWritingMode() ||
       style.direction() != ComputedStyle::initialDirection())
     return false;
   // The cache assumes static knowledge about which properties are inherited.
   // Without a flat tree parent, StyleBuilder::applyProperty will not
   // setHasExplicitlyInheritedProperties on the parent style.
   if (!state.parentNode() || parentStyle.hasExplicitlyInheritedProperties())
     return false;
   if (style.hasVariableReferenceFromNonInheritedProperty())
     return false;
+  if (style.hasFilter() && style.filter().hasReferenceFilter())

[esprehn, 2016/10/25 01:18:42]

Hmm, can you explain why you need to turn off matched properties caching here? I
wonder why we need a strong reference inside the style value. It seems like the
style should setup observations on the Document for things with the referenced
filter id?

[fs, 2016/10/25 15:00:53]

Because mutations to the DOM tree does not reflect in the MatchResults. I guess
optionally this could be handled out-of-band of the style system by having
clients register id observers?
There's only a strong reference to the proxy (and back.) The proxy is
essentially the "observation" mechanism. I guess for the actual target element
we could use IdTargetObservers and do away with the generation mechanism.

+    return false;
   return true;
 }
 
 DEFINE_TRACE(MatchedPropertiesCache) {
   visitor->trace(m_cache);
 }
 
 }  // namespace blink