Revert "Reverting custom pseudo element".

LayoutTests/fast/dom/shadow/custom-pseudo-in-selector-api.html

Index: LayoutTests/fast/dom/shadow/custom-pseudo-in-selector-api.html
diff --git a/LayoutTests/fast/dom/shadow/custom-pseudo-in-selector-api.html b/LayoutTests/fast/dom/shadow/custom-pseudo-in-selector-api.html
index d75d8d738368ab40cd7fff91301a3fc95c7b1b9a..ccda1a6f9431708eea9624247c929055ba8145ba 100644
--- a/LayoutTests/fast/dom/shadow/custom-pseudo-in-selector-api.html
+++ b/LayoutTests/fast/dom/shadow/custom-pseudo-in-selector-api.html
@@ -18,6 +18,20 @@ shouldBeNull('sandbox.firstChild.querySelector("input[type=\'search\']::-webkit-
 shouldBe('sandbox.firstChild.querySelectorAll("input[type=\'search\']::-webkit-search-decoration").length', '0');
 
 sandbox.innerHTML = '';
+
+sandbox.appendChild(
+    createDOM('div', {'id': 'host'},
+        createShadowRoot(
+            createDOM('div', {'pseudo': 'x-pseudo', 'part': 'x-part'}))));
+
+shouldBeFalse('sandbox.firstChild.webkitMatchesSelector("div::x-pseudo")');
+shouldBeFalse('sandbox.firstChild.webkitMatchesSelector("div::x-part")');
+shouldBeNull('sandbox.firstChild.querySelector("div::x-pseudo")');
+shouldBeNull('sandbox.firstChild.querySelector("div::x-part")');
+shouldBe('sandbox.firstChild.querySelectorAll("div::x-pseudo").length', '0');
+shouldBe('sandbox.firstChild.querySelectorAll("div::x-part").length', '0');
+
+sandbox.innerHTML = '';
 </script>
 </body>
 </html>