Make KeyboardEvent have direct fields for keyCode/charCode, as they're no longer inherited from UIE…

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 76e3a5a1f8952c7eab4951237be7962074899db7..c8ca2a9d4fb8bfbf34d72433985ee4e81a147b91 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -22176,10 +22176,10 @@ class KeyboardEvent extends UIEvent {
   }
 
   @DomName('KeyboardEvent.keyCode')
-  int get keyCode => _keyCode;
+  final int keyCode;
 
   @DomName('KeyboardEvent.charCode')
-  int get charCode => _charCode;
+  final int charCode;
 
   @DomName('KeyboardEvent.which')
   int get which => _which;