Make List an abstract class.

runtime/lib/array_patch.dart

Index: runtime/lib/array_patch.dart
diff --git a/runtime/lib/array_patch.dart b/runtime/lib/array_patch.dart
index 5bb7ec2c2ad176f5c4977b21ea7ea057bb63e02d..2887a994d7a07dbd7c43d6934e0144a6fbaa36d3 100644
--- a/runtime/lib/array_patch.dart
+++ b/runtime/lib/array_patch.dart
@@ -5,7 +5,7 @@
 // Note that the optimizing compiler depends on the algorithm which
 // returns a _GrowableObjectArray if length is null, otherwise returns
 // fixed size array.
-patch class _ListImpl<E> {
+patch class List<E> {
   /* patch */ factory List([int length = null]) {
     if (length == null) {
       return new _GrowableObjectArray<E>();
@@ -14,14 +14,6 @@ patch class _ListImpl<E> {
     }
   }
 
-  /* patch */ factory List.from(Iterable<E> other) {
-    _GrowableObjectArray<E> list = new _GrowableObjectArray<E>();
-    for (final e in other) {
-      list.add(e);
-    }
-    return list;
-  }
-
   // Factory constructing a mutable List from a parser generated List literal.
   // [elements] contains elements that are already type checked.
   factory List._fromLiteral(List elements) {