Fix monitor contention logging to support negative line numbers

Bug: 24743369
Change-Id: I8dd4f59e0bd27aa4daa1d79a412fc7821c070c67
diff --git a/runtime/monitor_linux.cc b/runtime/monitor_linux.cc
index 856ebe4..1c77ac0 100644
--- a/runtime/monitor_linux.cc
+++ b/runtime/monitor_linux.cc
@@ -18,7 +18,7 @@
 
 namespace art {
 
-void Monitor::LogContentionEvent(Thread*, uint32_t, uint32_t, const char*, uint32_t) {
+void Monitor::LogContentionEvent(Thread*, uint32_t, uint32_t, const char*, int32_t) {
 }
 
 }  // namespace art