Enable some parts of base that were previously disabled in base_untrusted

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 59162b92afeac0594945f96cfa57d94770a248b8..09159a293b50379d9ae4d4b13a90d89b3181f7b9 100644
--- a/base/threading/platform_thread_posix.cc
+++ b/base/threading/platform_thread_posix.cc
@@ -162,7 +162,9 @@ PlatformThreadId PlatformThread::CurrentId() {
   return gettid();
 #elif defined(OS_SOLARIS)
   return pthread_self();
-#elif defined(OS_NACL)
+#elif defined(OS_NACL) && defined(__GLIBC__)
+  return pthread_self();
+#elif defined(OS_NACL) && !defined(__GLIBC__)
   // Pointers are 32-bits in NaCl.
   return reinterpret_cast<int32>(pthread_self());
 #elif defined(OS_POSIX)