Fixing Element.matches to be cross-platform and follow latest spec.

sdk/lib/html/templates/html/impl/impl_Element.darttemplate

Index: sdk/lib/html/templates/html/impl/impl_Element.darttemplate
diff --git a/sdk/lib/html/templates/html/impl/impl_Element.darttemplate b/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
index fc2bcfb2b97b10c5e790c3be901f5586e85d8d67..d91420ea694ddd6a978e09846e2ab4ff85acc0b5 100644
--- a/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
+++ b/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
@@ -729,6 +729,22 @@ $if DART2JS
         throw new ArgumentError("Invalid position ${where}");
     }
   }
+
+  /**
+   * Checks if this element matches the CSS selectors.
+   */
+  @Experimental()
+  bool matches(String selectors) {
+    if (JS('bool', '!!#.matches', this)) {
+      return JS('bool', '#.matches(#)', this, selectors);
+    } else if (JS('bool', '!!#.webkitMatchesSelector', this)) {
+      return JS('bool', '#.webkitMatchesSelector(#)', this, selectors);
+    } else if (JS('bool', '!!#.mozMatchesSelector', this)) {
+      return JS('bool', '#.mozMatchesSelector(#)', this, selectors);
+    } else if (JS('bool', '!!#.msMatchesSelector', this)) {
+      return JS('bool', '#.msMatchesSelector(#)', this, selectors);
+    }
+  }
 $else
 $endif