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/test/912-classes/classes.cc b/test/912-classes/classes.cc
index 19d82c5..38a4f0e 100644
--- a/test/912-classes/classes.cc
+++ b/test/912-classes/classes.cc
@@ -29,6 +29,20 @@
 namespace art {
 namespace Test912Classes {
 
+extern "C" JNIEXPORT jboolean JNICALL Java_Main_isModifiableClass(
+    JNIEnv* env ATTRIBUTE_UNUSED, jclass Main_klass ATTRIBUTE_UNUSED, jclass klass) {
+  jboolean res = JNI_FALSE;
+  jvmtiError result = jvmti_env->IsModifiableClass(klass, &res);
+  if (result != JVMTI_ERROR_NONE) {
+    char* err;
+    jvmti_env->GetErrorName(result, &err);
+    printf("Failure running IsModifiableClass: %s\n", err);
+    jvmti_env->Deallocate(reinterpret_cast<unsigned char*>(err));
+    return JNI_FALSE;
+  }
+  return res;
+}
+
 extern "C" JNIEXPORT jobjectArray JNICALL Java_Main_getClassSignature(
     JNIEnv* env, jclass Main_klass ATTRIBUTE_UNUSED, jclass klass) {
   char* sig;