Always show login header bar on the account picker screen.

ui/login/account_picker/screen_account_picker.js

Index: ui/login/account_picker/screen_account_picker.js
diff --git a/ui/login/account_picker/screen_account_picker.js b/ui/login/account_picker/screen_account_picker.js
index 9823493208fa7bffea87db553b1dcae5792cb522..6a534ab9ce344bf9ae91dcf532b575abaedcbdd2 100644
--- a/ui/login/account_picker/screen_account_picker.js
+++ b/ui/login/account_picker/screen_account_picker.js
@@ -118,6 +118,8 @@ login.createScreen('AccountPickerScreen', 'account-picker', function() {
       this.showing_ = true;
       chrome.send('loginUIStateChanged', ['account-picker', true]);
       $('login-header-bar').signinUIState = SIGNIN_UI_STATE.ACCOUNT_PICKER;
+      // Header bar should be always visible on Account Picker screen.
+      Oobe.getInstance().headerHidden = false;
       chrome.send('hideCaptivePortal');
       var podRow = $('pod-row');
       podRow.handleBeforeShow();