Remove support for pseudo classes in <content select>.

LayoutTests/fast/selectors/style-sharing-shadow.html

Index: LayoutTests/fast/selectors/style-sharing-shadow.html
diff --git a/LayoutTests/fast/selectors/style-sharing-shadow.html b/LayoutTests/fast/selectors/style-sharing-shadow.html
index 152b07b2b82b25cdc0d2291ea7bd0477493d3ed9..676aab515d61eb123f2e9703e246dd9a620816a1 100644
--- a/LayoutTests/fast/selectors/style-sharing-shadow.html
+++ b/LayoutTests/fast/selectors/style-sharing-shadow.html
@@ -66,10 +66,10 @@
 
     var host6 = document.createElement('div');
     var root1 = host6.createShadowRoot();
-    root1.innerHTML = '<style>.foo::content > p { color: red; }</style><content class="foo" select=":first-child"></content><content></content>';
+    root1.innerHTML = '<style>.foo::content > p { color: red; }</style><content class="foo" select=".a"></content><content></content>';
     var root2 = host6.createShadowRoot();
     root2.innerHTML = '<shadow></shadow>';
-    host6.innerHTML = '<p>A</p><p>B</p>';
+    host6.innerHTML = '<p class="a">A</p><p>B</p>';
     container.appendChild(host6);
     document.body.offsetHeight;
     light = host6.querySelectorAll('p');