Change List constructors.

sdk/lib/_internal/compiler/implementation/lib/js_helper.dart

Index: sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart b/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
index 467f28e3edd24d79c3843c78b4aa4a68544d4dab..8508a4ced9500fdf5b2b4da59337e0f09a75db7d 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
@@ -512,14 +512,17 @@ class Primitives {
     return "Instance of '$name'";
   }
 
-  static List newList(length) {
+  static List newGrowableList(length) {
+    // TODO(sra): For good concrete type analysis we need the JS-type to
+    // specifically name the JavaScript Array implementation.  'List' matches
+    // all the dart:html types that implement List<T>.
+    return JS('Object', r'new Array(#)', length);
+  }
+
+  static List newFixedList(length) {
     // TODO(sra): For good concrete type analysis we need the JS-type to
     // specifically name the JavaScript Array implementation.  'List' matches
     // all the dart:html types that implement List<T>.
-    if (length == null) return JS('=List', r'new Array()');
-    if ((length is !int) || (length < 0)) {
-      throw new ArgumentError(length);
-    }
     var result = JS('=List', r'new Array(#)', length);
     JS('void', r'#.fixed$length = #', result, true);
     return result;