Supervised user blacklist: Make the cmdline flag an enable/disable type.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 35d3d8b52cf4410f04b39b2da3ea7df1d08ae1a0..4886c0ddb38a956c26f3e2b73ac763b6d8f96999 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -346,6 +346,10 @@ const char kDisableSpdy31[]                 = "disable-spdy31";
 // Disables the suggestions service.
 const char kDisableSuggestionsService[]     = "disable-suggestions-service";
 
+// Disables the supervised user host blacklist.
+const char kDisableSupervisedUserBlacklist[] =
+    "disable-supervised-user-blacklist";
+
 // Disables syncing browser data to a Google Account.
 const char kDisableSync[]                   = "disable-sync";