Remove ThrowLocation.

Note that this is a cleanup change, and has no functionality change.
The ThrowLocation had no use anymore.

Change-Id: I3d2126af1dc673cec3a0453ff3d56a172663a5f6
diff --git a/runtime/native/java_lang_Thread.cc b/runtime/native/java_lang_Thread.cc
index e4b8db1..d3b52ba 100644
--- a/runtime/native/java_lang_Thread.cc
+++ b/runtime/native/java_lang_Thread.cc
@@ -100,7 +100,7 @@
   ScopedObjectAccess soa(env);
   mirror::Object* object = soa.Decode<mirror::Object*>(java_object);
   if (object == NULL) {
-    ThrowNullPointerException(NULL, "object == null");
+    ThrowNullPointerException("object == null");
     return JNI_FALSE;
   }
   MutexLock mu(soa.Self(), *Locks::thread_list_lock_);