Add missing SIRT to LoadNativeLibrary.

When we transition to kWaitingForJniOnLoad, we are suspended and
a GC can occur. This caused issues since classloaders are movable.

Change-Id: Iae59019c22ac64322a82300107d06a4323ee602b
diff --git a/runtime/native/java_lang_Runtime.cc b/runtime/native/java_lang_Runtime.cc
index e969fcf..0629f4d 100644
--- a/runtime/native/java_lang_Runtime.cc
+++ b/runtime/native/java_lang_Runtime.cc
@@ -64,7 +64,8 @@
   std::string detail;
   {
     ScopedObjectAccess soa(env);
-    mirror::ClassLoader* classLoader = soa.Decode<mirror::ClassLoader*>(javaLoader);
+    SirtRef<mirror::ClassLoader> classLoader(soa.Self(),
+                                             soa.Decode<mirror::ClassLoader*>(javaLoader));
     JavaVMExt* vm = Runtime::Current()->GetJavaVM();
     bool success = vm->LoadNativeLibrary(filename.c_str(), classLoader, &detail);
     if (success) {