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..a52617690bd0d877299a745f4bfc15195f9ca3f7 100644
--- a/sandbox/linux/services/credentials.h
+++ b/sandbox/linux/services/credentials.h
@@ -39,9 +39,9 @@ class SANDBOX_EXPORT Credentials {
   // 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();
+  // MoveToNewUserNS() immediately. This method is only useful to test the
+  // ability to move to a user namespace ahead of time.
+  static bool CanCreateProcessInNewUserNS();
 
   // Move the current process to a new "user namespace" as supported by Linux
   // 3.8+ (CLONE_NEWUSER).