Support getComputedStyle for non-rendered 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 aec2f6ac9612dc5eb0a2dcbb793d62c909ed005e..76765cc6a397a56c849e2e4d58503308dd99dd12 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -2398,26 +2398,32 @@ RenderStyle* Element::computedStyle(PseudoId pseudoElementSpecifier)
     if (PseudoElement* element = pseudoElement(pseudoElementSpecifier))
         return element->computedStyle();
 
+    if (!inActiveDocument()) {
+        // FIXME: Try to do better than this. Ensure that styleForElement() works for elements that are not in the
+        // document tree and figure out when to destroy the computed style for such elements.
+        return 0;
+    }
+
     // FIXME: Find and use the renderer from the pseudo element instead of the actual element so that the 'length'
     // properties, which are only known by the renderer because it did the layout, will be correct and so that the
     // values returned for the ":selection" pseudo-element will be correct.
-    if (RenderStyle* usedStyle = renderStyle()) {
-        if (pseudoElementSpecifier) {
-            RenderStyle* cachedPseudoStyle = usedStyle->getCachedPseudoStyle(pseudoElementSpecifier);
-            return cachedPseudoStyle ? cachedPseudoStyle : usedStyle;
-         } else
-            return usedStyle;
+    RenderStyle* elementStyle = renderStyle();
+    if (!elementStyle) {
+        ElementRareData& rareData = ensureElementRareData();
+        if (!rareData.computedStyle())
+            rareData.setComputedStyle(document().styleForElementIgnoringPendingStylesheets(this));
+        elementStyle = rareData.computedStyle();
     }
 
-    if (!inActiveDocument())
-        // FIXME: Try to do better than this. Ensure that styleForElement() works for elements that are not in the
-        // document tree and figure out when to destroy the computed style for such elements.
-        return 0;
+    if (!pseudoElementSpecifier)
+        return elementStyle;
 
-    ElementRareData& rareData = ensureElementRareData();
-    if (!rareData.computedStyle())
-        rareData.setComputedStyle(document().styleForElementIgnoringPendingStylesheets(this));
-    return pseudoElementSpecifier ? rareData.computedStyle()->getCachedPseudoStyle(pseudoElementSpecifier) : rareData.computedStyle();
+    if (RenderStyle* pseudoElementStyle = elementStyle->getCachedPseudoStyle(pseudoElementSpecifier))
+        return pseudoElementStyle;
+
+    RefPtr<RenderStyle> result = document().ensureStyleResolver().pseudoStyleForElement(this, PseudoStyleRequest(pseudoElementSpecifier, PseudoStyleRequest::ForComputedStyle), elementStyle);
+    ASSERT(result);
+    return elementStyle->addCachedPseudoStyle(result.release());
 }
 
 AtomicString Element::computeInheritedLanguage() const