[Mac] In PlatformThread::CurrentId(), use pthread_self() instead of mach_thread_self().

base/threading/platform_thread_posix.cc

Index: base/threading/platform_thread_posix.cc
diff --git a/base/threading/platform_thread_posix.cc b/base/threading/platform_thread_posix.cc
index 7eda4e97c51169bc28b7fef49ca7466e1ed4eaf2..27e666a870deaf5758d0512abc273563022e90d6 100644
--- a/base/threading/platform_thread_posix.cc
+++ b/base/threading/platform_thread_posix.cc
@@ -16,7 +16,6 @@
 #include "base/tracked_objects.h"
 
 #if defined(OS_MACOSX)
-#include <mach/mach.h>
 #include <sys/resource.h>
 #include <algorithm>
 #endif
@@ -132,11 +131,7 @@ bool CreateThread(size_t stack_size, bool joinable,
 PlatformThreadId PlatformThread::CurrentId() {
   // Pthreads doesn't have the concept of a thread ID, so we have to reach down
   // into the kernel.
-#if defined(OS_MACOSX)
-  mach_port_t port = mach_thread_self();
-  mach_port_deallocate(mach_task_self(), port);
-  return port;
-#elif defined(OS_LINUX)
+#if defined(OS_LINUX)
   return syscall(__NR_gettid);
 #elif defined(OS_ANDROID)
   return gettid();