List marker pseudo elements.

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 9c192f2eaceb76e32a6280ccf10d7a2832dac874..8795e694bd2e7a11dfadeb9ef33c47c73c76f8cb 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -70,6 +70,7 @@
 #include "core/css/resolver/ViewportStyleResolver.h"
 #include "core/dom/CSSSelectorWatch.h"
 #include "core/dom/FirstLetterPseudoElement.h"
+#include "core/dom/MarkerPseudoElement.h"
 #include "core/dom/NodeComputedStyle.h"
 #include "core/dom/StyleEngine.h"
 #include "core/dom/Text.h"
@@ -713,25 +714,41 @@ PassRefPtrWillBeRawPtr<AnimatableValue> StyleResolver::createAnimatableValueSnap
 
 PassRefPtrWillBeRawPtr<PseudoElement> StyleResolver::createPseudoElement(Element* parent, PseudoId pseudoId)
 {
+    if (RuntimeEnabledFeatures::listMarkerPseudoElementEnabled() && pseudoId == MARKER)
+        return MarkerPseudoElement::create(parent);
     if (pseudoId == FIRST_LETTER)
         return FirstLetterPseudoElement::create(parent);
     return PseudoElement::create(parent, pseudoId);
 }
 
+bool StyleResolver::pseudoElementRequired(PseudoId pseudoId, LayoutObject& parentRenderer)
+{
+    if (pseudoId == FIRST_LETTER)
+        return true;
+    if (RuntimeEnabledFeatures::listMarkerPseudoElementEnabled() && pseudoId == MARKER)
+        return true;
+    if (parentRenderer.style()->hasPseudoStyle(pseudoId))
+        return true;
+    return pseudoId >= FIRST_INTERNAL_PSEUDOID;
+}
+
 PassRefPtrWillBeRawPtr<PseudoElement> StyleResolver::createPseudoElementIfNeeded(Element& parent, PseudoId pseudoId)
 {
     LayoutObject* parentRenderer = parent.layoutObject();
     if (!parentRenderer)
         return nullptr;
 
-    // The first letter pseudo element has to look up the tree and see if any
-    // of the ancestors are first letter.
-    if (pseudoId < FIRST_INTERNAL_PSEUDOID && pseudoId != FIRST_LETTER && !parentRenderer->style()->hasPseudoStyle(pseudoId))
+    if (!pseudoElementRequired(pseudoId, *parentRenderer))
         return nullptr;
 
     if (pseudoId == BACKDROP && !parent.isInTopLayer())
         return nullptr;
 
+    // FIXME: This should also probably take inline-list-item into account when
+    // we add support.
+    if (RuntimeEnabledFeatures::listMarkerPseudoElementEnabled() && pseudoId == MARKER && parentRenderer->style()->display() != LIST_ITEM)
+        return nullptr;
+
     if (pseudoId == FIRST_LETTER && (parent.isSVGElement() || !FirstLetterPseudoElement::firstLetterTextRenderer(parent)))
         return nullptr;
 
@@ -801,10 +818,11 @@ bool StyleResolver::pseudoStyleForElementInternal(Element& element, const Pseudo
         matchUARules(collector);
         matchAuthorRules(state.element(), collector, false);
 
-        if (collector.matchedResult().matchedProperties.isEmpty())
+        if (!collector.matchedResult().matchedProperties.isEmpty())
+            applyMatchedProperties(state, collector.matchedResult());
+        else if (pseudoStyleRequest.pseudoId != MARKER || parentStyle->display() != LIST_ITEM)
             return false;
 
-        applyMatchedProperties(state, collector.matchedResult());
         applyCallbackSelectors(state);
 
         // Cache our original display.