Rename :ancestor to :host-context.

LayoutTests/fast/dom/shadow/hostcontext-first-child.html

Index: LayoutTests/fast/dom/shadow/hostcontext-first-child.html
diff --git a/LayoutTests/fast/dom/shadow/ancestor-first-child.html b/LayoutTests/fast/dom/shadow/hostcontext-first-child.html
similarity index 79%
rename from LayoutTests/fast/dom/shadow/ancestor-first-child.html
rename to LayoutTests/fast/dom/shadow/hostcontext-first-child.html
index ebccd8424d67390c09d8082e040f55a85d76ecff..4381432bdfe765906cddca3708448471e7561a4b 100644
--- a/LayoutTests/fast/dom/shadow/ancestor-first-child.html
+++ b/LayoutTests/fast/dom/shadow/hostcontext-first-child.html
@@ -7,7 +7,7 @@
 </div>
 
 <script>
-description("Test that :ancestor(:first-child) is re-evaluated when :first-child changes.");
+description("Test that :host-context(:first-child) is re-evaluated when :first-child changes.");
 
 var test = document.getElementById("test");
 var first = document.getElementById("first");
@@ -16,7 +16,7 @@ first.appendChild(
     createDOM("div", {"id": "host"},
         createShadowRoot(
             createDOM('style', {},
-                document.createTextNode(":ancestor(#first:first-child) { background-color: red; }")),
+                document.createTextNode(":host-context(#first:first-child) { background-color: red; }")),
             createDOM('div', {},
                 document.createTextNode("You should see no red.")))));