Optimize style recalc when adding @keyframes.

third_party/WebKit/Source/core/animation/AnimationTimeline.cpp

Index: third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
diff --git a/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp b/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
index e753bba98fa8b3a49529b1a33c63b0ac6a7b02af..da5f7c5883a91c13f418dfa075dc7a0cc6c522ee 100644
--- a/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
+++ b/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
@@ -33,6 +33,7 @@
 #include "core/animation/AnimationClock.h"
 #include "core/animation/ElementAnimations.h"
 #include "core/dom/Document.h"
+#include "core/dom/StyleChangeReason.h"
 #include "core/frame/FrameView.h"
 #include "core/loader/DocumentLoader.h"
 #include "core/page/Page.h"
@@ -347,6 +348,25 @@ double AnimationTimeline::playbackRate() const
     return m_playbackRate;
 }
 
+void AnimationTimeline::keyframesRulesAdded()
+{
+    if (m_hasUnresolvedKeyframesRule) {
+        m_hasUnresolvedKeyframesRule = false;
+        if (m_document)
+            m_document->setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::Animation));
+        return;
+    }
+
+    for (const auto& animation : m_animations) {
+        const AnimationEffect* effect = animation->effect();
+        if (!effect)
+            continue;
+        if (!effect->isKeyframeEffect())
+            continue;
+        toKeyframeEffect(effect)->target()->setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::Animation));
+    }
+}
+
 DEFINE_TRACE(AnimationTimeline)
 {
     visitor->trace(m_document);