First pass at cleaning up html lib warnings from the analyzer.

tools/dom/src/KeyboardEventStream.dart

 // Copyright (c) 2012, 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.
 
 part of html;
 
 /**
  * Internal class that does the actual calculations to determine keyCode and
  * charCode for keydown, keypress, and keyup events for all browsers.
  */
@@ skipping 58 matching lines @@
     var handler = new _KeyboardEventHandler.initializeAllEventListeners(
         _type, e);
     return handler._stream;
   }
 
   /**
    * General constructor, performs basic initialization for our improved
    * KeyboardEvent controller.
    */
   _KeyboardEventHandler(this._type): super(_EVENT_TYPE),
-      _stream = new _CustomKeyEventStreamImpl('event');
+      _stream = new _CustomKeyEventStreamImpl('event'), _target = null;
 
   /**
    * Hook up all event listeners under the covers so we can estimate keycodes
    * and charcodes when they are not provided.
    */
   _KeyboardEventHandler.initializeAllEventListeners(this._type, this._target) :
       super(_EVENT_TYPE) {
     Element.keyDownEvent.forTarget(_target, useCapture: true).listen(
         processKeyDown);
     Element.keyPressEvent.forTarget(_target, useCapture: true).listen(
@@ skipping 282 matching lines @@
       new _KeyboardEventHandler('keypress').forTarget(target);
 
   /** Named constructor to produce a stream for onKeyUp events. */
   static CustomStream<KeyEvent> onKeyUp(EventTarget target) =>
       new _KeyboardEventHandler('keyup').forTarget(target);
 
   /** Named constructor to produce a stream for onKeyDown events. */
   static CustomStream<KeyEvent> onKeyDown(EventTarget target) =>
       new _KeyboardEventHandler('keydown').forTarget(target);
 }