Mac build fixes I missed in my previous patch.

Change-Id: Ibf63e77b9e18374fa802b508c9e489105a88e017
diff --git a/src/monitor.h b/src/monitor.h
index 0a8c795..4d73e37 100644
--- a/src/monitor.h
+++ b/src/monitor.h
@@ -122,7 +122,7 @@
   // sampling is enabled. locking_method_ may be null if the lock is currently
   // unlocked, or if the lock is acquired by the system when the stack is empty.
   const Method* locking_method_;
-  uint32_t locking_pc_;
+  uintptr_t locking_pc_;
 
   friend class MonitorList;
   friend class Object;