Fix various warnings and errors in html_diff and its annotations.

client/html/html.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // DO NOT EDIT
 // Auto-generated Dart HTML library.
 
 #library('html');
 
 #import('dart:dom', prefix:'dom');
@@ skipping 149 matching lines @@
 #source('generated/src/interface/Int16Array.dart');
 #source('generated/src/interface/Int32Array.dart');
 #source('generated/src/interface/Int8Array.dart');
 #source('generated/src/interface/JavaScriptAudioNode.dart');
 #source('generated/src/interface/KeygenElement.dart');
 #source('generated/src/interface/LIElement.dart');
 #source('generated/src/interface/LabelElement.dart');
 #source('generated/src/interface/LegendElement.dart');
 #source('generated/src/interface/LinkElement.dart');
 #source('generated/src/interface/Location.dart');
-#source('generated/src/interface/LoseContext.dart');
 #source('generated/src/interface/LowPass2FilterNode.dart');
 #source('generated/src/interface/MapElement.dart');
 #source('generated/src/interface/MarqueeElement.dart');
 #source('generated/src/interface/MediaElement.dart');
 #source('generated/src/interface/MediaElementAudioSourceNode.dart');
 #source('generated/src/interface/MediaError.dart');
 #source('generated/src/interface/MediaList.dart');
 #source('generated/src/interface/MediaQueryList.dart');
 #source('generated/src/interface/MediaQueryListListener.dart');
 #source('generated/src/interface/MenuElement.dart');
@@ skipping 258 matching lines @@
 #source('src/DOMApplicationCache.dart');
 #source('src/Element.dart');
 #source('src/ErrorEvent.dart');
 #source('src/Event.dart');
 #source('src/EventListener.dart');
 #source('src/EventSource.dart');
 #source('src/EventTarget.dart');
 #source('src/GlobalProperties.dart');
 #source('src/HashChangeEvent.dart');
 #source('src/KeyboardEvent.dart');
+#source('src/LoseContext.dart');
 #source('src/MessageEvent.dart');
 #source('src/MessagePort.dart');
 #source('src/MouseEvent.dart');
 #source('src/MutationEvent.dart');
 #source('src/Node.dart');
 #source('src/NodeList.dart');
 #source('src/Notification.dart');
 #source('src/ObjectElement.dart');
 #source('src/OverflowEvent.dart');
 #source('src/PageTransitionEvent.dart');
@@ skipping 12 matching lines @@
 #source('src/TouchEvent.dart');
 #source('src/TransitionEvent.dart');
 #source('src/UIEvent.dart');
 #source('src/WebSocket.dart');
 #source('src/WheelEvent.dart');
 #source('src/Window.dart');
 #source('src/Worker.dart');
 #source('src/XMLHttpRequest.dart');
 #source('src/XMLHttpRequestProgressEvent.dart');
 #source('src/XMLHttpRequestUpload.dart');