Add a button to exit managed mode.

chrome/browser/managed_mode.cc

Index: chrome/browser/managed_mode.cc
diff --git a/chrome/browser/managed_mode.cc b/chrome/browser/managed_mode.cc
index 15706a8edfe79bff9c569c7e806246d55818ae37..fa4f303fa9525d7dff21c10343f4f70f625590f3 100644
--- a/chrome/browser/managed_mode.cc
+++ b/chrome/browser/managed_mode.cc
@@ -41,6 +41,9 @@ bool ManagedMode::IsInManagedModeImpl() {
   // |g_browser_process| can be NULL during startup.
   if (!g_browser_process)
     return false;
+  // Local State can be NULL during unit tests.
+  if (!g_browser_process->local_state())
+    return false;
   return g_browser_process->local_state()->GetBoolean(prefs::kInManagedMode);
 }