List marker pseudo elements.

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index b120e748a731d37a75f2f9e19dd732ca6e6816a8..8a7ddb7e75eff5e608f98bd52da3d5d3a2ea2113 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -1525,6 +1525,11 @@ void Element::attach(const AttachContext& context)
     // from any of them.
     createPseudoElementIfNeeded(FIRST_LETTER);
 
+    // The marker has to come after the other content, including the BEFORE pseudo
+    // element so make sure we create it last.
+    if (RuntimeEnabledFeatures::listMarkerPseudoElementEnabled())
+        createPseudoElementIfNeeded(MARKER);
+
     if (hasRareData() && !layoutObject()) {
         if (ElementAnimations* elementAnimations = elementRareData()->elementAnimations()) {
             elementAnimations->cssAnimations().cancel();
@@ -1691,6 +1696,8 @@ void Element::recalcStyle(StyleRecalcChange change, Text* nextTextSibling)
 
         updatePseudoElement(AFTER, change);
         updatePseudoElement(BACKDROP, change);
+        if (RuntimeEnabledFeatures::listMarkerPseudoElementEnabled())
+            updatePseudoElement(MARKER, change);
 
         // If our children have changed then we need to force the first-letter
         // checks as we don't know if they effected the first letter or not.
@@ -2757,9 +2764,12 @@ void Element::updatePseudoElement(PseudoId pseudoId, StyleRecalcChange change)
         // Wait until our parent is not displayed or pseudoElementRendererIsNeeded
         // is false, otherwise we could continuously create and destroy PseudoElements
         // when LayoutObject::isChildAllowed on our parent returns false for the
-        // PseudoElement's renderer for each style recalc.
-        if (!layoutObject() || !pseudoElementRendererIsNeeded(layoutObject()->getCachedPseudoStyle(pseudoId)))
+        // PseudoElement's layoutObject for each style recalc.
+        if (!layoutObject()
+            || (!pseudoElementRendererIsNeeded(layoutObject()->getCachedPseudoStyle(pseudoId))
+                && (pseudoId == MARKER && layoutObject()->style()->display() != LIST_ITEM))) {

[esprehn, 2015/04/22 07:45:45]

What's up with this check for != LIST_ITEM all over?

[dsinclair, 2015/04/22 20:00:38]

If you have something like: <div style="display: list-item"> it will have a
MARKER, but, we then change to display:block we're going to have a MARKER but no
longer be a list item. In that case, we have to destroy the MARKER as it's no
longer valid.

             elementRareData()->setPseudoElement(pseudoId, nullptr);
+        }
     } else if (pseudoId == FIRST_LETTER && element && change >= UpdatePseudoElements && !FirstLetterPseudoElement::firstLetterTextRenderer(*element)) {
         // This can happen if we change to a float, for example. We need to cleanup the
         // first-letter pseudoElement and then fix the text of the original remaining
@@ -2793,16 +2803,16 @@ bool Element::updateFirstLetter(Element* element)
 
 void Element::createPseudoElementIfNeeded(PseudoId pseudoId)
 {
-    if (isPseudoElement())
+    if (isPseudoElement() && (pseudoId != MARKER || isMarkerPseudoElement()))

[esprehn, 2015/04/22 07:45:45]

Marker shouldn't need a special case here. PseudoElements can never have nested
pseudo elements. This branch doesn't need to change.

[dsinclair, 2015/04/22 20:00:38]

With marker they can. If we have something like:

    #a:after {
        display: list-item;
        content: "ONE";
    }

Then the ::after pseudo element will have a ::marker pseudo element under it.
Added a comment.

         return;
 
     // Document::ensureStyleResolver is not inlined and shows up on profiles, avoid it here.
-    RefPtrWillBeRawPtr<PseudoElement> element = document().styleEngine().ensureResolver().createPseudoElementIfNeeded(*this, pseudoId);
+    RefPtrWillBeRawPtr<PseudoElement> element =  document().styleEngine().ensureResolver().createPseudoElementIfNeeded(*this, pseudoId);
     if (!element)
         return;
-
     if (pseudoId == BACKDROP)
         document().addToTopLayer(element.get(), this);
+
     element->insertedInto(this);
     element->attach();