Add test to check that IsArray returns true for immutable array objects.

runtime/vm/object_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 "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
 #include "vm/isolate.h"
@@ skipping 1652 matching lines @@
 
   other_array.SetAt(1, other_array);
   EXPECT(!array.Equals(other_array));
 
   other_array = Array::New(kArrayLen - 1);
   other_array.SetAt(0, array);
   other_array.SetAt(2, array);
   EXPECT(!array.Equals(other_array));
 
   EXPECT_EQ(0, Object::empty_array().Length());
+
+  array.MakeImmutable();
+  Object& obj = Object::Handle(array.raw());
+  ASSERT(obj.IsArray());
 }
 
 
 TEST_CASE(StringCodePointIterator) {
   const String& str0 = String::Handle(String::New(""));
   String::CodePointIterator it0(str0);
   EXPECT(!it0.Next());
 
   const String& str1 = String::Handle(String::New(" \xc3\xa7 "));
   String::CodePointIterator it1(str1);
@@ skipping 1638 matching lines @@
   const Function& test7 = Function::Handle(GetFunction(class_a, "test7"));
   EXPECT_EQ(test1.SourceFingerprint(), test2.SourceFingerprint());
   EXPECT_NE(test1.SourceFingerprint(), test3.SourceFingerprint());
   EXPECT_NE(test3.SourceFingerprint(), test4.SourceFingerprint());
   EXPECT_NE(test4.SourceFingerprint(), test5.SourceFingerprint());
   EXPECT_NE(test5.SourceFingerprint(), test6.SourceFingerprint());
   EXPECT_EQ(test6.SourceFingerprint(), test7.SourceFingerprint());
 }
 
 }  // namespace dart