Fixing visibilityState APIs in Dart

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 6887091dacdf3c07dd1f361bc3d69e8aa8a648cd..e4aaa299ee5ef524046ce8adca1f751137468ea7 100644
--- a/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
+++ b/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
@@ -160,11 +160,18 @@ $endif
   Element get pointerLockElement =>
       _webkitPointerLockElement;
 
-  @DomName('Document.webkitVisibilityState')
+  @DomName('Document.visibilityState')
   @SupportedBrowser(SupportedBrowser.CHROME)
-  @SupportedBrowser(SupportedBrowser.SAFARI)
+  @SupportedBrowser(SupportedBrowser.FIREFOX)
+  @SupportedBrowser(SupportedBrowser.IE, '10')
   @Experimental()
+$if DART2JS
+  String get visibilityState => JS('String',
+    '(#.visibilityState || #.mozVisibilityState || #.msVisibilityState ||'
+      '#.webkitVisibilityState)', this, this, this, this);
+$else
   String get visibilityState => _webkitVisibilityState;
+$endif
 
   @Experimental
 $if DART2JS
@@ -182,4 +189,38 @@ $if DART2JS
 $endif
   // Note: used to polyfill <template>
   Document _templateContentsOwner;
+
+  @DomName('Document.visibilityChange')
+  @SupportedBrowser(SupportedBrowser.CHROME)
+  @SupportedBrowser(SupportedBrowser.FIREFOX)
+  @SupportedBrowser(SupportedBrowser.IE, '10')
+  @Experimental()
+  static const EventStreamProvider<Event> visibilityChangeEvent =
+      const _CustomEventStreamProvider<Event>(
+        _determineVisibilityChangeEventType);
+
+  static String _determineVisibilityChangeEventType(EventTarget e) {
+$if DART2JS
+    if (JS('bool', '(typeof #.hidden !== "undefined")', e)) {
+      // Opera 12.10 and Firefox 18 and later support
+      return 'visibilitychange';
+    } else if (JS('bool', '(typeof #.mozHidden !== "undefined")', e)) {
+      return 'mozvisibilitychange';
+    } else if (JS('bool', '(typeof #.msHidden !== "undefined")', e)) {
+      return 'msvisibilitychange';
+    } else if (JS('bool', '(typeof #.webkitHidden !== "undefined")', e)) {
+      return 'webkitvisibilitychange';
+    }
+    return 'visibilitychange';
+$else
+    return 'webkitvisibilitychange';
+$endif
+  }
+
+  @SupportedBrowser(SupportedBrowser.CHROME)
+  @SupportedBrowser(SupportedBrowser.FIREFOX)
+  @SupportedBrowser(SupportedBrowser.IE, '10')
+  @Experimental()
+  Stream<Event> get onVisibilityChange =>
+      visibilityChangeEvent.forTarget(this);
 }