Reapply r18377 it was reverted due to the unrelated bug it surfaced.

runtime/vm/object.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 "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
@@ skipping 2167 matching lines @@
   }
   // Check for reflexivity.
   if (raw() == other.raw()) {
     const intptr_t len = NumTypeArguments();
     if (len == 0) {
       return true;
     }
     // Since we do not truncate the type argument vector of a subclass (see
     // below), we only check a prefix of the proper length.
     // Check for covariance.
-    if (other_type_arguments.IsNull() ||
-        other_type_arguments.IsRawInstantiatedRaw(len)) {
+    if (other_type_arguments.IsNull() || other_type_arguments.IsRaw(len)) {
       return true;
     }
-    if (type_arguments.IsNull() ||
-        type_arguments.IsRawInstantiatedRaw(len)) {
+    if (type_arguments.IsNull() || type_arguments.IsRaw(len)) {
+      // Other type can't be more specific than this one because for that
+      // it would have to have all dynamic type arguments which is checked
+      // above.
       return test_kind == kIsSubtypeOf;
     }
     return type_arguments.TypeTest(test_kind,
                                    other_type_arguments,
                                    len,
                                    malformed_error);
   }
   const bool other_is_function_class = other.IsFunctionClass();
   if (other.IsSignatureClass() || other_is_function_class) {
     const Function& other_fun = Function::Handle(other.signature_function());
@@ skipping 10589 matching lines @@
   }
   return result.raw();
 }
 
 
 const char* WeakProperty::ToCString() const {
   return "_WeakProperty";
 }
 
 }  // namespace dart