Make PopSirt inlinable, pass self to SirtRef.

Change-Id: Ieb91526b1cb1f8644ceb3c5b99649f658f43bbc1
diff --git a/src/object_utils.h b/src/object_utils.h
index 035f689..1d66c8f 100644
--- a/src/object_utils.h
+++ b/src/object_utils.h
@@ -32,8 +32,8 @@
 
 class ObjectLock {
  public:
-  explicit ObjectLock(Object* object) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
-      : self_(Thread::Current()), obj_(object) {
+  explicit ObjectLock(Thread* self, Object* object) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
+      : self_(self), obj_(object) {
     CHECK(object != NULL);
     obj_->MonitorEnter(self_);
   }