Remove use of IterableMixinWorkaround from _List, _ImmutableList and _GrowableList.

runtime/vm/debugger_api_impl_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_debugger_api.h"
 #include "include/dart_mirrors_api.h"
 #include "platform/assert.h"
 #include "vm/dart_api_impl.h"
 #include "vm/lockers.h"
 #include "vm/unit_test.h"
@@ skipping 2238 matching lines @@
   result = Dart_Invoke(lib, NewString("testMain"), 0, NULL);
   EXPECT_VALID(result);
 
   // First ensure that the returned object is a list.
   Dart_Handle list_access_test_obj = result;
   EXPECT(Dart_IsList(list_access_test_obj));
 
   Dart_Handle list_type = Dart_InstanceGetType(list_access_test_obj);
   Dart_Handle super_type = Dart_GetSupertype(list_type);
   EXPECT(!Dart_IsError(super_type));
-  super_type = Dart_GetSupertype(super_type);
-  EXPECT(!Dart_IsError(super_type));
-  EXPECT(super_type == Dart_Null());
 }
 
 TEST_CASE(Debug_ScriptGetTokenInfo_Basic) {
   const char* kScriptChars =
       "var foo;\n"
       "\n"
       "main() {\n"
       "}";
 
   Dart_Handle lib = TestCase::LoadTestScript(kScriptChars, NULL);
@@ skipping 43 matching lines @@
       " null, 3, 7, 1, 8, 6, 9, 10, 10, 11, 11, 13,"
       " null, 4, 13, 3, 14, 10,"
       " null, 5, 17, 5, 18, 9, 19, 12,"
       " null, 6, 21, 1,"
       " null, 8, 24, 1, 25, 5, 26, 6, 27, 8,"
       " null, 9, 29, 1]",
       tokens_cstr);
 }
 
 }  // namespace dart