Refactor the setuid sandbox client code to its own class.

base/linux_util.h

Index: base/linux_util.h
diff --git a/base/linux_util.h b/base/linux_util.h
index 3009a655c45873b33422bca4bcb9c5484effe3fb..b9ba56dfc970ce45173bf8706ec37bdb8f9ef38e 100644
--- a/base/linux_util.h
+++ b/base/linux_util.h
@@ -16,11 +16,6 @@ namespace base {
 
 BASE_EXPORT extern const char kFindInodeSwitch[];
 
-// This should be kept in sync with sandbox/linux/suid/sandbox.c
-BASE_EXPORT extern const long kSUIDSandboxApiNumber;
-BASE_EXPORT extern const char kSandboxEnvironmentApiRequest[];
-BASE_EXPORT extern const char kSandboxEnvironmentApiProvides[];
-
 // This is declared here so the crash reporter can access the memory directly
 // in compromised context without going through the standard library.
 BASE_EXPORT extern char g_linux_distro[];