Optimize style recalc when adding @keyframes.

third_party/WebKit/Source/core/dom/StyleEngine.cpp

Index: third_party/WebKit/Source/core/dom/StyleEngine.cpp
diff --git a/third_party/WebKit/Source/core/dom/StyleEngine.cpp b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
index b7cccd69a0808c85471a3698915ce9c4f613368e..80728018d5fcf036180b8a15f05f172f64ace92f 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngine.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
@@ -28,6 +28,7 @@
 #include "core/dom/StyleEngine.h"
 
 #include "core/HTMLNames.h"
+#include "core/animation/AnimationTimeline.h"
 #include "core/css/CSSDefaultStyleSheets.h"
 #include "core/css/CSSFontSelector.h"
 #include "core/css/CSSStyleSheet.h"
@@ -743,6 +744,17 @@ void StyleEngine::ensureFullscreenUAStyle()
         m_resolver->resetRuleFeatures();
 }
 
+void StyleEngine::keyframesRulesAdded()
+{
+    if (m_hasUnresolvedKeyframesRule) {
+        m_hasUnresolvedKeyframesRule = false;
+        document().setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::StyleSheetChange));
+        return;
+    }
+
+    document().timeline().invalidateKeyframeEffects();
+}
+
 DEFINE_TRACE(StyleEngine)
 {
     visitor->trace(m_document);