Support :hover/:active in quirks when leftmost in compound.

LayoutTests/fast/css/hover-pseudo-element-quirks.html

+<!-- quirks mode -->
+<script src="../../resources/js-test.js"></script>
+<style>
+:hover::before, :hover::after { background-color: green }
+#t1::before { content: "Green background when hovered" }
+#t2::after { content: "Green background when hovered" }
+</style>
+<div id="t1"></div>
+<div id="t2"></div>
+<script>
+description("Quirks mode - universal :hover on pseudo elements");
+
+function moveTo(element) {
+    eventSender.mouseMoveTo(element.offsetLeft + 1,  element.offsetTop + 1);
+}
+
+var transparent = "rgba(0, 0, 0, 0)";
+var green = "rgb(0, 128, 0)";
+
+shouldBeDefined("window.eventSender");
+
+shouldBe("getComputedStyle(t1, '::before').backgroundColor", "transparent");
+moveTo(t1);
+shouldBe("getComputedStyle(t1, '::before').backgroundColor", "green");
+
+shouldBe("getComputedStyle(t2, '::after').backgroundColor", "transparent");
+moveTo(t2);
+shouldBe("getComputedStyle(t2, '::after').backgroundColor", "green");
+</script>