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

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index e75ea5d2cb596cca41336b7f6be9662c935035c4..ab1afab7e9090b91ba35848a8da0a87d3fca673a 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -12175,6 +12175,9 @@ class LocalWindow extends EventTarget implements Window native "@*DOMWindow" {
   /** @domName Window.atob */
   String atob(String string) native;
 
+  /** @domName Window.blur */
+  void blur() native;
+
   /** @domName Window.btoa */
   String btoa(String string) native;
 
@@ -12199,6 +12202,9 @@ class LocalWindow extends EventTarget implements Window native "@*DOMWindow" {
   /** @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";
 
@@ -22258,6 +22264,8 @@ abstract class Window {
   Window get top;
 
   // Methods.
+  void focus();
+  void blur();
   void close();
   void postMessage(var message, String targetOrigin, [List messagePorts = null]);
 }