Don't push selector filter for pseudo elements.

Pseudo elements match the features of its originating element. We were
pushing the selector filter too early causing fast rejection glitches
when matching selectors for pseudo elements.

Change-Id: I04bc1d7e681ecd6c851bdb3820a9950003e0821d
Reviewed-on: https://chromium-review.googlesource.com/1148201
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Anders Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577664}

third_party/blink/renderer/core/css/style_engine_test.cc

@@ -1472,4 +1472,32 @@ TEST_F(StyleEngineTest, GetComputedStyleOutsideFlatTreeCrash) {
   GetDocument().View()->UpdateAllLifecyclePhases();
 }
 
+TEST_F(StyleEngineTest, RejectSelectorForPseudoElement) {
+  GetDocument().body()->SetInnerHTMLFromString(R"HTML(
+    <style>
+      div::before { content: "" }
+      .not-in-filter div::before { color: red }
+    </style>
+    <div class='not-in-filter'></div>
+  )HTML");
+  GetDocument().View()->UpdateAllLifecyclePhases();
+
+  StyleEngine& engine = GetDocument().GetStyleEngine();
+  engine.SetStatsEnabled(true);
+
+  StyleResolverStats* stats = engine.Stats();
+  ASSERT_TRUE(stats);
+
+  Element* div = GetDocument().QuerySelector("div");
+  ASSERT_TRUE(div);
+  div->SetInlineStyleProperty(CSSPropertyColor, "green");
+
+  GetDocument().Lifecycle().AdvanceTo(DocumentLifecycle::kInStyleRecalc);
+  GetDocument().documentElement()->RecalcStyle(kNoChange);
+
+  // Should fast reject ".not-in-filter div::before {}" for both the div and its
+  // ::before pseudo element.
+  EXPECT_EQ(2u, stats->rules_fast_rejected);
+}
+
 }  // namespace blink

third_party/blink/renderer/core/dom/element.cc

@@ -2349,14 +2349,11 @@ void Element::RecalcStyle(StyleRecalcChange change) {
   }
 
   if (ShouldCallRecalcStyleForChildren(change)) {
-    // TODO(futhark@chromium.org): Pseudo elements are feature-less and match
-    // the same features as their originating element. Move the filter scope
-    // inside the if-block for shadow-including descendants below.
-    SelectorFilterParentScope filter_scope(*this);
 
     UpdatePseudoElement(kPseudoIdBefore, change);
 
     if (change > kUpdatePseudoElements || ChildNeedsStyleRecalc()) {
+      SelectorFilterParentScope filter_scope(*this);
       if (ShadowRoot* root = GetShadowRoot()) {
         if (root->ShouldCallRecalcStyle(change))
           root->RecalcStyle(change);