chromeos: Break WebUILoginDisplay and SigninScreenHandler coupling on destruction.

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
index 106521af27755abdf39b2c5aaf1ecbdfe238e47c..9da9b23aef0e33fd6d5ccdb015aaaa2790c5538f 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -288,6 +288,8 @@ SigninScreenHandler::~SigninScreenHandler() {
     cookie_remover_->RemoveObserver(this);
   if (key_event_listener_)
     key_event_listener_->RemoveCapsLockObserver(this);
+  if (delegate_)
+    delegate_->SetWebUIHandler(NULL);
   CrosSettings::Get()->RemoveSettingsObserver(kAccountsPrefAllowNewUser, this);
   CrosSettings::Get()->RemoveSettingsObserver(kAccountsPrefAllowGuest, this);
 }
@@ -536,6 +538,10 @@ void SigninScreenHandler::ShowGaiaPasswordChanged(const std::string& username) {
       "login.AccountPickerScreen.updateUserGaiaNeeded", email_value);
 }
 
+void SigninScreenHandler::ResetSigninScreenHandlerDelegate() {
+  SetDelegate(NULL);
+}
+
 void SigninScreenHandler::OnBrowsingDataRemoverDone() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   cookie_remover_ = NULL;