Adding @keyframes rules only affects TreeScope plus host.

third_party/WebKit/Source/core/css/resolver/StyleResolver.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/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 1141 matching lines @@
     return true;
 }
 
 StyleRuleKeyframes* StyleResolver::findKeyframesRule(const Element* element, const AtomicString& animationName)
 {
     HeapVector<Member<ScopedStyleResolver>, 8> resolvers;
     collectScopedResolversForHostedShadowTrees(*element, resolvers);
     if (ScopedStyleResolver* scopedResolver = element->treeScope().scopedStyleResolver())
         resolvers.append(scopedResolver);
 
-    for (size_t i = 0; i < resolvers.size(); ++i) {
-        if (StyleRuleKeyframes* keyframesRule = resolvers[i]->keyframeStylesForAnimation(animationName.impl()))
+    for (auto& resolver : resolvers) {
+        if (StyleRuleKeyframes* keyframesRule = resolver->keyframeStylesForAnimation(animationName.impl()))
             return keyframesRule;
     }
+
+    for (auto& resolver : resolvers)
+        resolver->setHasUnresolvedKeyframesRule();
     return nullptr;
 }
 
 template <CSSPropertyPriority priority>
 void StyleResolver::applyAnimatedProperties(StyleResolverState& state, const ActiveInterpolationsMap& activeInterpolationsMap)
 {
     // TODO(alancutter): Don't apply presentation attribute animations here,
     // they should instead apply in SVGElement::collectStyleForPresentationAttribute().
     for (const auto& entry : activeInterpolationsMap) {
         CSSPropertyID property = entry.key.isCSSProperty() ? entry.key.cssProperty() : entry.key.presentationAttribute();
@@ skipping 567 matching lines @@
     visitor->trace(m_siblingRuleSet);
     visitor->trace(m_uncommonAttributeRuleSet);
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingScopes);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 }
 
 } // namespace blink