dom: more final more of the time

sdk/lib/chrome/dart2js/chrome_dart2js.dart

Index: sdk/lib/chrome/dart2js/chrome_dart2js.dart
diff --git a/sdk/lib/chrome/dart2js/chrome_dart2js.dart b/sdk/lib/chrome/dart2js/chrome_dart2js.dart
index 7c1ca62c055bfb3011c3bcea61dcc6c7e30b395f..2c416c4c77bb9b70c11009167930468a435172ed 100644
--- a/sdk/lib/chrome/dart2js/chrome_dart2js.dart
+++ b/sdk/lib/chrome/dart2js/chrome_dart2js.dart
@@ -59,7 +59,7 @@ abstract class ChromeObject {
   /*
    * JS Object Representation
    */
-  Object _jsObject;
+  final Object _jsObject;
 }
 
 /**
@@ -196,12 +196,12 @@ class Event {
   /*
    * JS Object Representation
    */
-  Object _jsObject;
+  final Object _jsObject;
 
   /*
    * Number of arguments the callback takes.
    */
-  int _callbackArity;
+  final int _callbackArity;
 
   /*
    * Private constructor
@@ -329,7 +329,7 @@ class API_ChromeApp {
   /*
    * JS Variable
    */
-  Object _jsObject;
+  final Object _jsObject;
 
   /*
    * Members