Revert "Removed Window.focus and Window.blur as they are no longer recommended."

sdk/lib/html/dart2js/html_dart2js.dart

 library html;
 
 import 'dart:isolate';
 import 'dart:json';
 import 'dart:svg' as svg;
 // 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.
 
 // DO NOT EDIT
@@ skipping 12157 matching lines @@
 
   /** @domName Window.addEventListener */
   void $dom_addEventListener(String type, EventListener listener, [bool useCapture]) native "addEventListener";
 
   /** @domName Window.alert */
   void alert(String message) native;
 
   /** @domName Window.atob */
   String atob(String string) native;
 
+  /** @domName Window.blur */
+  void blur() native;
+
   /** @domName Window.btoa */
   String btoa(String string) native;
 
   /** @domName Window.captureEvents */
   void captureEvents() native;
 
   /** @domName Window.clearInterval */
   void clearInterval(int handle) native;
 
   /** @domName Window.clearTimeout */
   void clearTimeout(int handle) native;
 
   /** @domName Window.close */
   void close() native;
 
   /** @domName Window.confirm */
   bool confirm(String message) native;
 
   /** @domName Window.dispatchEvent */
   bool $dom_dispatchEvent(Event evt) native "dispatchEvent";
 
   /** @domName Window.find */
   bool find(String string, bool caseSensitive, bool backwards, bool wrap, bool wholeWord, bool searchInFrames, bool showDialog) native;
 
+  /** @domName Window.focus */
+  void focus() native;
+
   /** @domName Window.getComputedStyle */
   CSSStyleDeclaration $dom_getComputedStyle(Element element, String pseudoElement) native "getComputedStyle";
 
   /** @domName Window.getMatchedCSSRules */
   List<CSSRule> getMatchedCSSRules(Element element, String pseudoElement) native;
 
   /** @domName Window.getSelection */
   DOMSelection getSelection() native;
 
   /** @domName Window.matchMedia */
@@ skipping 10039 matching lines @@
    *     myIFrame.elements.add(innerIFrame);
    *
    *     print(myIframe.contentWindow.top == window) // 'true'
    *     print(innerIFrame.contentWindow.top == window) // 'true'
    *
    *     print(window.top == window) // 'true'
    */
   Window get top;
 
   // Methods.
+  void focus();
+  void blur();
   void close();
   void postMessage(var message, String targetOrigin, [List messagePorts = null]);
 }
 
 abstract class Location {
   void set href(String val);
 }
 
 abstract class History {
   void back();
@@ skipping 2840 matching lines @@
     if (length < 0) throw new ArgumentError('length');
     if (start < 0) throw new RangeError.value(start);
     int end = start + length;
     if (end > a.length) throw new RangeError.value(end);
     for (int i = start; i < end; i++) {
       accumulator.add(a[i]);
     }
     return accumulator;
   }
 }