Fetch array length before dropping vm access

Rather than dropping access, only to acquire and release it
during the `env->GetArrayLength` call, use the macro to
avoid the extra in and out of vm access

Signed-off-by: Dan Heidinga <heidinga@redhat.com>

runtime/jcl/common/sun_misc_Unsafe.cpp

@@ -119,12 +119,12 @@ Java_sun_misc_Unsafe_defineAnonymousClass(JNIEnv *env, jobject receiver, jclass
 		}
 	}
 
-	vmFuncs->internalExitVMToJNI(currentThread);
+	jsize length = (jsize)J9INDEXABLEOBJECT_SIZE(currentThread, J9_JNI_UNWRAP_REFERENCE(bytecodes));
 
-	jsize length = env->GetArrayLength(bytecodes);
+	vmFuncs->internalExitVMToJNI(currentThread);
 
 	/* acquires access internally */
-	jclass anonClass = defineClassCommon(env, hostClassLoaderLocalRef, NULL,bytecodes, 0, length, protectionDomainLocalRef, &defineClassOptions, hostClazz, &cpPatchMap, FALSE);
+	jclass anonClass = defineClassCommon(env, hostClassLoaderLocalRef, NULL, bytecodes, 0, length, protectionDomainLocalRef, &defineClassOptions, hostClazz, &cpPatchMap, FALSE);
 	if (env->ExceptionCheck()) {
 		return NULL;
 	} else if (NULL == anonClass) {