Revert "Move toString() to collection classes."

sdk/lib/_internal/lib/js_array.dart

Index: sdk/lib/_internal/lib/js_array.dart
diff --git a/sdk/lib/_internal/lib/js_array.dart b/sdk/lib/_internal/lib/js_array.dart
index 5718c5d47314f6aca5154b2d5c99d27f2a76628f..36685a4be65a7c3bc8f65822d1d1ad33ad6be298 100644
--- a/sdk/lib/_internal/lib/js_array.dart
+++ b/sdk/lib/_internal/lib/js_array.dart
@@ -11,11 +11,10 @@ part of _interceptors;
  * argument added to each member.
  */
 class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
-
   const JSArray();
 
   checkMutable(reason) {
-    if (this is !JSMutableArray) {
+    if (this is !JSMutableArray) { 
       throw new UnsupportedError(reason);
     }
   }
@@ -262,7 +261,7 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
 
   bool get isNotEmpty => !isEmpty;
 
-  String toString() => IterableMixinWorkaround.toStringIterable(this, '[', ']');
+  String toString() => ToString.iterableToString(this);
 
   List<E> toList({ bool growable: true }) =>
       new List<E>.from(this, growable: growable);