Linux sandbox: cleanup sandbox-bpf naming.

sandbox/linux/seccomp-bpf/die.cc

Index: sandbox/linux/seccomp-bpf/die.cc
diff --git a/sandbox/linux/seccomp-bpf/die.cc b/sandbox/linux/seccomp-bpf/die.cc
index 594740c7792734181c76b93324a6e5e1a6bc1eff..533e2e9c353e3cc02e8cc0254a364165665b25a1 100644
--- a/sandbox/linux/seccomp-bpf/die.cc
+++ b/sandbox/linux/seccomp-bpf/die.cc
@@ -14,7 +14,7 @@
 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #include "sandbox/linux/seccomp-bpf/syscall.h"
 
-namespace playground2 {
+namespace sandbox {
 
 void Die::ExitGroup() {
   // exit_group() should exit our program. After all, it is defined as a
@@ -82,4 +82,4 @@ void Die::LogToStderr(const char* msg, const char* file, int line) {
 bool Die::simple_exit_ = false;
 bool Die::suppress_info_ = false;
 
-}  // namespace
+}  // namespace sandbox