Consistently use base::OpenFile.

Change-Id: Ib9275182c984084f1d4f7e63faf380888b3c0a76
diff --git a/src/base/watchdog_posix.cc b/src/base/watchdog_posix.cc
index d8c064c..85cbb96 100644
--- a/src/base/watchdog_posix.cc
+++ b/src/base/watchdog_posix.cc
@@ -127,7 +127,7 @@
 }
 
 void Watchdog::ThreadMain() {
-  base::ScopedFile stat_fd(open("/proc/self/stat", O_RDONLY));
+  base::ScopedFile stat_fd(base::OpenFile("/proc/self/stat", O_RDONLY));
   if (!stat_fd) {
     PERFETTO_ELOG("Failed to open stat file to enforce resource limits.");
     return;