Move a couple of utility functions to a new namespace_utils class.

sandbox/linux/services/credentials.h

Index: sandbox/linux/services/credentials.h
diff --git a/sandbox/linux/services/credentials.h b/sandbox/linux/services/credentials.h
index fc65afcd5f6c7e39786f0439a45b0364deaeac78..06ff8fd9a078a225398bd6d54250dcc0e52ab77d 100644
--- a/sandbox/linux/services/credentials.h
+++ b/sandbox/linux/services/credentials.h
@@ -36,13 +36,6 @@ class SANDBOX_EXPORT Credentials {
   // debugging and tests.
   static scoped_ptr<std::string> GetCurrentCapString();
 
-  // Returns whether the kernel supports CLONE_NEWUSER and whether it would be
-  // possible to immediately move to a new user namespace. There is no point
-  // in using this method right before calling MoveToNewUserNS(), simply call
-  // MoveToNewUserNS() immediately. This method is only useful to test kernel
-  // support ahead of time.
-  static bool SupportsNewUserNS();

[jln (very slow on Chromium), 2015/01/23 02:48:23]

I wonder if we should keep this as "CanCreateProcessInNewUserNS"?

[rickyz (no longer on Chrome), 2015/01/23 23:59:37]

Done - at this point, there pretty messy separation of responsibility between
namespace_utils.cc and credentials.cc - I'll try to clean this up after getting
the non-setuid sandbox in.

-
   // Move the current process to a new "user namespace" as supported by Linux
   // 3.8+ (CLONE_NEWUSER).
   // The uid map will be set-up so that the perceived uid and gid will not