Revert "Fix a few strong mode errors in dart:html"

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

Index: tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate b/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
index 11a8d8d6de2e3c0ecd1966a65dcd6cf649687426..a52e369a14c8682d4c39a5de0842d88ba9ee5a9b 100644
--- a/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
+++ b/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
@@ -152,6 +152,22 @@ $endif
   @Experimental()
   Element get fullscreenElement => _webkitFullscreenElement;
 
+  /**
+   * Returns true if this document can display elements in fullscreen mode.
+   *
+   * ## Other resources
+   *
+   * * [Using the fullscreen
+   *   API](http://docs.webplatform.org/wiki/tutorials/using_the_full-screen_api)
+   *   from WebPlatform.org.
+   * * [Fullscreen specification](http://www.w3.org/TR/fullscreen/) from W3C.
+   */
+  @DomName('Document.webkitFullscreenEnabled')
+  @SupportedBrowser(SupportedBrowser.CHROME)
+  @SupportedBrowser(SupportedBrowser.SAFARI)
+  @Experimental()
+  bool get fullscreenEnabled => _webkitFullscreenEnabled;
+
   @DomName('Document.webkitHidden')
   @SupportedBrowser(SupportedBrowser.CHROME)
   @SupportedBrowser(SupportedBrowser.SAFARI)