Disable StubTest.IndexOf if heap poisoning is enabled for now.

art_quick_indexof does not support heap poisoning yet.

Bug: 12687968
Change-Id: Ibc497cc782399f0d8e0d3dca59e1ebb358fe83a5
diff --git a/runtime/arch/stub_test.cc b/runtime/arch/stub_test.cc
index 7785bc3..22b8cca 100644
--- a/runtime/arch/stub_test.cc
+++ b/runtime/arch/stub_test.cc
@@ -1796,6 +1796,8 @@
 
 TEST_F(StubTest, StringIndexOf) {
 #if defined(__arm__) || defined(__aarch64__)
+  TEST_DISABLED_FOR_HEAP_REFERENCE_POISONING();
+
   Thread* self = Thread::Current();
   ScopedObjectAccess soa(self);
   // garbage is created during ClassLinker::Init