Skip rule matching during animations.

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index 526c7f1f286fc268e23c518a069b7fcb7df2c1e4..b87413d17046d6af584e4cf82417ca9f59492074 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -578,7 +578,12 @@ PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderS
             return sharedStyle.release();
     }
 
-    if (state.parentStyle()) {
+    ActiveAnimations* activeAnimations = element->activeAnimations();
+    const RenderStyle* baseRenderStyle = activeAnimations ? activeAnimations->baseRenderStyle() : nullptr;
+
+    if (baseRenderStyle) {
+        state.setStyle(RenderStyle::clone(baseRenderStyle));
+    } else if (state.parentStyle()) {
         state.setStyle(RenderStyle::create());
         state.style()->inheritFrom(state.parentStyle(), isAtShadowBoundary(element) ? RenderStyle::AtShadowBoundary : RenderStyle::NotAtShadowBoundary);
     } else {
@@ -607,12 +612,13 @@ PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderS
         state.style()->setInsideLink(linkState);
     }
 
-    bool needsCollection = false;
-    CSSDefaultStyleSheets::instance().ensureDefaultStyleSheetsForElement(element, needsCollection);
-    if (needsCollection)
-        collectFeatures();
+    if (!baseRenderStyle) {
+
+        bool needsCollection = false;
+        CSSDefaultStyleSheets::instance().ensureDefaultStyleSheetsForElement(element, needsCollection);
+        if (needsCollection)
+            collectFeatures();
 
-    {
         ElementRuleCollector collector(state.elementContext(), m_selectorFilter, state.style());
 
         matchAllRules(state, collector, matchingBehavior != MatchAllRulesExcludingSMIL);
@@ -621,12 +627,15 @@ PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderS
         applyCallbackSelectors(state);
 
         addContentAttrValuesToFeatures(state.contentAttrValues(), m_features);
-    }
 
-    // Cache our original display.
-    state.style()->setOriginalDisplay(state.style()->display());
+        // Cache our original display.
+        state.style()->setOriginalDisplay(state.style()->display());
 
-    adjustRenderStyle(state, element);
+        adjustRenderStyle(state, element);
+
+        if (activeAnimations)
+            activeAnimations->updateBaseRenderStyle(state.style());
+    }
 
     // FIXME: The CSSWG wants to specify that the effects of animations are applied before
     // important rules, but this currently happens here as we require adjustment to have happened
@@ -761,7 +770,14 @@ bool StyleResolver::pseudoStyleForElementInternal(Element& element, const Pseudo
 
     StyleResolverParentScope::ensureParentStackIsPushed();
 
-    if (pseudoStyleRequest.allowsInheritance(state.parentStyle())) {
+    Element* pseudoElement = element.pseudoElement(pseudoStyleRequest.pseudoId);
+
+    ActiveAnimations* activeAnimations = pseudoElement ? pseudoElement->activeAnimations() : nullptr;
+    const RenderStyle* baseRenderStyle = activeAnimations ? activeAnimations->baseRenderStyle() : nullptr;
+
+    if (baseRenderStyle) {
+        state.setStyle(RenderStyle::clone(baseRenderStyle));
+    } else if (pseudoStyleRequest.allowsInheritance(state.parentStyle())) {
         state.setStyle(RenderStyle::create());
         state.style()->inheritFrom(state.parentStyle());
     } else {
@@ -775,7 +791,7 @@ bool StyleResolver::pseudoStyleForElementInternal(Element& element, const Pseudo
     // Since we don't use pseudo-elements in any of our quirk/print
     // user agent rules, don't waste time walking those rules.
 
-    {
+    if (!baseRenderStyle) {
         // Check UA, user and author rules.
         ElementRuleCollector collector(state.elementContext(), m_selectorFilter, state.style());
         collector.setPseudoStyleRequest(pseudoStyleRequest);
@@ -790,19 +806,22 @@ bool StyleResolver::pseudoStyleForElementInternal(Element& element, const Pseudo
         applyCallbackSelectors(state);
 
         addContentAttrValuesToFeatures(state.contentAttrValues(), m_features);
-    }
 
-    // Cache our original display.
-    state.style()->setOriginalDisplay(state.style()->display());
+        // Cache our original display.
+        state.style()->setOriginalDisplay(state.style()->display());
 
-    // FIXME: Passing 0 as the Element* introduces a lot of complexity
-    // in the adjustRenderStyle code.
-    adjustRenderStyle(state, 0);
+        // FIXME: Passing 0 as the Element* introduces a lot of complexity
+        // in the adjustRenderStyle code.
+        adjustRenderStyle(state, 0);
+
+        if (activeAnimations)
+            activeAnimations->updateBaseRenderStyle(state.style());
+    }
 
     // FIXME: The CSSWG wants to specify that the effects of animations are applied before
     // important rules, but this currently happens here as we require adjustment to have happened
     // before deciding which properties to transition.
-    if (applyAnimatedProperties(state, element.pseudoElement(pseudoStyleRequest.pseudoId)))
+    if (applyAnimatedProperties(state, pseudoElement))
         adjustRenderStyle(state, 0);
 
     didAccess();