8072588: JVM crashes in JNI if toString is declared as an interface method

Check for a valid itable index instead of checking if the holder is an interface

Reviewed-by: dsimms, dholmes

hotspot/test/runtime/jni/ToStringInInterfaceTest/ToStringTest.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8072588
+ * @build InterfaceWithToString
+ * @build ImplementationOfWithToString
+ * @run main/native ToStringTest
+ */
+public final class ToStringTest {
+
+    static {
+        System.loadLibrary("ToStringTest");
+    }
+
+    native static void nTest();
+
+    public static void main(String[] args) throws Exception {
+        nTest();
+    }
+}