Allow signin to continue even if sync is disabled by policy.

chrome/browser/signin/about_signin_internals.cc

Index: chrome/browser/signin/about_signin_internals.cc
diff --git a/chrome/browser/signin/about_signin_internals.cc b/chrome/browser/signin/about_signin_internals.cc
index e75d3ef53c9a436cd90e1aa04ea566a708adbc68..e58570ece5e7aa421251defbd9694ad1575b91d6 100644
--- a/chrome/browser/signin/about_signin_internals.cc
+++ b/chrome/browser/signin/about_signin_internals.cc
@@ -204,10 +204,15 @@ void AboutSigninInternals::Initialize(Profile* profile) {
 }
 
 void AboutSigninInternals::Shutdown() {
-  SigninManagerFactory::GetForProfile(profile_)->
-      RemoveSigninDiagnosticsObserver(this);
-  TokenServiceFactory::GetForProfile(profile_)->
-      RemoveSigninDiagnosticsObserver(this);
+  SigninManager* signin = SigninManagerFactory::GetForProfile(profile_);
+  // Some unit tests do stuff like switching profiles to incognito in mid-test,
+  // so there may not always be
+  if (signin)
+    signin->RemoveSigninDiagnosticsObserver(this);
+
+  TokenService* token = TokenServiceFactory::GetForProfile(profile_);
+  if (token)
+    token->RemoveSigninDiagnosticsObserver(this);
 }
 
 void AboutSigninInternals::NotifyObservers() {