Revert "Revert "Add basic implementation of IsModifiableClass""

This reverts commit c66c077d40db58ec239f93a9c42b9939439c85c7.

Reason for revert: Problem with preceding CL fixed.

Test: mma -j40 test-art-host
diff --git a/runtime/openjdkjvmti/OpenjdkJvmTi.cc b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
index d364d6e..c472b54 100644
--- a/runtime/openjdkjvmti/OpenjdkJvmTi.cc
+++ b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
@@ -599,7 +599,7 @@
   static jvmtiError IsModifiableClass(jvmtiEnv* env,
                                       jclass klass,
                                       jboolean* is_modifiable_class_ptr) {
-    return ERR(NOT_IMPLEMENTED);
+    return Redefiner::IsModifiableClass(env, klass, is_modifiable_class_ptr);
   }
 
   static jvmtiError GetClassLoader(jvmtiEnv* env, jclass klass, jobject* classloader_ptr) {