Improve return type of markUnmodifiableList to JSArray instead of List.

R=sgjesse@google.com

Review URL: https://codereview.chromium.org//1076013006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@45372 260f80e4-7a28-3924-810f-c04153c831b5

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Core library changes
 
+ * Add `unmodifiable` constructor to `List` class - 
+   [r45334](https://code.google.com/p/dart/source/detail?r=45334),
 * Update experimental Isolate API:
   - Make priorty parameters of `Isolate.ping` and `Isolate.kill` methods
     a named parameter.
@@ -14,7 +16,7 @@
 
 ### Core library changes
 
-* Fix behavior of `HtmlEscape` in `dart:convert`. No longer escape
+* Fix behavior of `HtmlEscape` in `dart:convert`. It no longer escapes
   no-break space (U+00A0) anywhere or forward slash ('/', U+002F) in element
   context. Slash is still escaped in the "unknown" context.
   [r45003](https://code.google.com/p/dart/source/detail?r=45003),

sdk/lib/_internal/compiler/js_lib/js_array.dart

@@ -83,7 +83,8 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
     // to know if the property exists.
     JS('void', r'#.fixed$length = Array', list);
     JS('void', r'#.immutable$list = Array', list);
-    return JS('List', '#', list);
+    // TODO(23309): Make it detectable that the list has fixed length.
+    return JS('JSArray', '#', list);
   }
 
   checkMutable(reason) {

sdk/lib/internal/list.dart

@@ -361,7 +361,7 @@ abstract class NonGrowableListError {
  * That means that it is a destructive conversion.
  * The original list should not be used afterwards.
  *
- * The returned list may be the same list as the orginal,
+ * The returned list may be the same list as the original,
  * or it may be a different list (according to [identical]).
  * The original list may have changed type to be a fixed list,
  * or become empty or been otherwise modified.
@@ -387,6 +387,6 @@ external List makeListFixedLength(List growableList);
  * That means that it is a destructive conversion.
  * The original list should not be used afterwards.
  *
- * The unmodifialbe list type is similar to the one used by const lists.
+ * The unmodifiable list type is similar to the one used by const lists.
  */
 external List makeFixedListUnmodifiable(List fixedLengthList);