Adding supported checks for Element.matches.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index e1340e28788fdb9e9865eb1eb867808bbfe2a2f4..ad2b8914d2f4de463bf6c5ba20c0787dfa20fa9d 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -8654,7 +8654,18 @@ abstract class Element extends Node implements ElementTraversal native "*Element
 
   /**
    * Checks if this element matches the CSS selectors.
+   *
+   * Use [supportsMatches] to check if this is supported on the current
+   * platform.
+   *
+   * See also:
+   *
+   * * [supportsMatches]
    */
+  @SupportedBrowser(SupportedBrowser.CHROME)
+  @SupportedBrowser(SupportedBrowser.FIREFOX)
+  @SupportedBrowser(SupportedBrowser.IE, '10')
+  @SupportedBrowser(SupportedBrowser.SAFARI)
   @Experimental
   bool matches(String selectors) {
     if (JS('bool', '!!#.matches', this)) {
@@ -8668,6 +8679,19 @@ abstract class Element extends Node implements ElementTraversal native "*Element
     }
   }
 
+  /**
+   * Checks if the matches function is supported on the current platform.
+   *
+   * See also:
+   *
+   * * [matches]
+   */
+  static bool get supportsMatches {
+    var e = new DivElement();
+    return JS('bool', '!!(#.matches || #.webkitMatchesSelector || '
+      '#.mozMatchesSelector || #.msMatchesSelector)', e, e, e, e);
+  }
+
 
   @DomName('Element.abort')
   @DocsEditable