Adding supported checks for Element.matches.

tools/dom/templates/html/impl/impl_Element.darttemplate

Index: tools/dom/templates/html/impl/impl_Element.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Element.darttemplate b/tools/dom/templates/html/impl/impl_Element.darttemplate
index b554609c25a574d0d8b2ca83d67ff216d9dd1d45..41dd22b49ee35b496f55c2e46c6b737a2bd8c4f8 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -895,7 +895,18 @@ $if DART2JS
 
   /**
    * 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)) {
@@ -908,7 +919,28 @@ $if DART2JS
       return JS('bool', '#.msMatchesSelector(#)', this, selectors);
     }
   }
+
+  /**
+   * 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);
+  }
 $else
+  /**
+   * Checks if the matches function is supported on the current platform.
+   *
+   * See also:
+   *
+   * * [matches]
+   */
+  static bool get supportsMatches => true;
 $endif
 
 $!MEMBERS