Remove =List in JS, use JSExtendableArray instead.

sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart

Index: sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(revision 24212)
+++ sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(working copy)
@@ -692,8 +692,6 @@
       TypeMask mappedType;
       if (type == native.SpecialType.JsObject) {
         mappedType = new TypeMask.nonNullExact(rawTypeOf(compiler.objectClass));
-      } else if (type == native.SpecialType.JsArray) {
-        mappedType = listType;
       } else if (type.element == compiler.stringClass) {
         mappedType = stringType;
       } else if (type.element == compiler.intClass) {
@@ -710,10 +708,10 @@
         mappedType = nullType;
       } else if (type.isDynamic) {
         return dynamicType;
-      } else if (compiler.world.hasAnySubclass(type.element)) {
-        mappedType = new TypeMask.nonNullSubclass(rawTypeOf(type.element));
       } else if (compiler.world.hasAnySubtype(type.element)) {
         mappedType = new TypeMask.nonNullSubtype(rawTypeOf(type.element));
+      } else if (compiler.world.hasAnySubclass(type.element)) {
+        mappedType = new TypeMask.nonNullSubclass(rawTypeOf(type.element));
       } else {
         mappedType = new TypeMask.nonNullExact(rawTypeOf(type.element));
       }