Add namespace sandbox class.

sandbox/linux/services/namespace_utils_unittest.cc

Index: sandbox/linux/services/namespace_utils_unittest.cc
diff --git a/sandbox/linux/services/namespace_utils_unittest.cc b/sandbox/linux/services/namespace_utils_unittest.cc
index 33ead9423c3bbc0233b34317a47072e301b1b222..42b469d8bbbb748a6ad62b594db48b2c01da59c8 100644
--- a/sandbox/linux/services/namespace_utils_unittest.cc
+++ b/sandbox/linux/services/namespace_utils_unittest.cc
@@ -45,11 +45,11 @@ SANDBOX_TEST(NamespaceUtils, WriteToIdMapFile) {
   ASSERT_NE(-1, pid);
   if (pid == 0) {
     RAW_CHECK(getuid() != uid);

[jln (very slow on Chromium), 2015/02/02 18:54:45]

These can be CHECKs (just need to _exit and not exit()).

Using RAW_CHECK is a little scary here: it looks like a bug given that
WriteToIdMapFile is not async signal safe.

[rickyz (no longer on Chrome), 2015/02/02 21:35:31]

Looks like WriteToIdMapFile not being async-signal-safe was a bug - that's fixed
now.

[jln (very slow on Chromium), 2015/02/03 01:14:30]

I don't think this code here needs to be async safe though.

-    NamespaceUtils::WriteToIdMapFile("/proc/self/uid_map", uid);
+    RAW_CHECK(NamespaceUtils::WriteToIdMapFile("/proc/self/uid_map", uid));
     RAW_CHECK(getuid() == uid);
 
     RAW_CHECK(getgid() != gid);
-    NamespaceUtils::WriteToIdMapFile("/proc/self/gid_map", gid);
+    RAW_CHECK(NamespaceUtils::WriteToIdMapFile("/proc/self/gid_map", gid));
     RAW_CHECK(getgid() == gid);
 
     _exit(0);