Use PathService to get temp dir name for IPC unittests.

ipc/unix_domain_socket_util_unittest.cc

Index: ipc/unix_domain_socket_util_unittest.cc
diff --git a/ipc/unix_domain_socket_util_unittest.cc b/ipc/unix_domain_socket_util_unittest.cc
index 813d4979260a611d67ecdc564898713b92b746c7..a8e9794cd2218fe8534779d807d43ba6fa471a6c 100644
--- a/ipc/unix_domain_socket_util_unittest.cc
+++ b/ipc/unix_domain_socket_util_unittest.cc
@@ -78,13 +78,9 @@ class SocketAcceptor : public base::MessageLoopForIO::Watcher {
 };
 
 const base::FilePath GetChannelDir() {
-#if defined(OS_ANDROID)
   base::FilePath tmp_dir;
-  PathService::Get(base::DIR_CACHE, &tmp_dir);
+  PathService::Get(base::DIR_TEMP, &tmp_dir);
   return tmp_dir;
-#else
-  return base::FilePath("/var/tmp");
-#endif
 }
 
 class TestUnixSocketConnection {