fuchsia: base_unittests (mostly) compiling

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 d9ee1ff7af57a8a7f6f8f647bc0961e229965514..e049a549d23cf52c09e143fef87bc66afe1e1fbe 100644
--- a/base/threading/platform_thread_posix.cc
+++ b/base/threading/platform_thread_posix.cc
@@ -137,7 +137,7 @@ PlatformThreadId PlatformThread::CurrentId() {
   return syscall(__NR_gettid);
 #elif defined(OS_ANDROID)
   return gettid();
-#elif defined(OS_SOLARIS) || defined(OS_QNX)
+#elif defined(OS_SOLARIS) || defined(OS_QNX) || defined(OS_FUCHSIA)
   return pthread_self();
 #elif defined(OS_NACL) && defined(__GLIBC__)
   return pthread_self();