Make List an abstract class.

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

Index: sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
index 5c6cb3bbe6ee7f8a38ba7532fc3d4730c0287a00..21cf6e1cdc0ab1da24c328f97f139632d7ae5214 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
@@ -154,16 +154,8 @@ patch class _StopwatchImpl {
 
 
 // Patch for List implementation.
-patch class _ListImpl<E> {
+patch class List<E> {
   patch factory List([int length]) => Primitives.newList(length);
-
-  patch factory List.from(Iterable<E> other) {
-    var result = new List();
-    for (var element in other) {
-      result.add(element);
-    }
-    return result;
-  }
 }