Adding @keyframes rules only affects TreeScope plus host.

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

Index: third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
index 8905d091bce27a3401b0b2131877252b7d7fa1b5..18f7ee6507696d6655130835571f321e462566f3 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
@@ -1159,10 +1159,13 @@ StyleRuleKeyframes* StyleResolver::findKeyframesRule(const Element* element, con
     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;
 }