Delete global ref created for the JitProfileTask.

We don't need it once the JitProfileTask is done.

Test: test.py && jitzygote boot
Change-Id: Ida75aeafa85a3f24dd22166aa8b2b296d7ae197a
diff --git a/runtime/jit/jit.cc b/runtime/jit/jit.cc
index d8399b4..1f734fe 100644
--- a/runtime/jit/jit.cc
+++ b/runtime/jit/jit.cc
@@ -697,6 +697,11 @@
     delete this;
   }
 
+  ~JitProfileTask() {
+    ScopedObjectAccess soa(Thread::Current());
+    soa.Vm()->DeleteGlobalRef(soa.Self(), class_loader_);
+  }
+
  private:
   std::vector<const DexFile*> dex_files_;
   jobject class_loader_;