Cleanup: Pull some browser keep alive functions into its own file.

chrome/browser/chromeos/login/ui/login_display_host_impl.h

Index: chrome/browser/chromeos/login/ui/login_display_host_impl.h
diff --git a/chrome/browser/chromeos/login/ui/login_display_host_impl.h b/chrome/browser/chromeos/login/ui/login_display_host_impl.h
index 55e6c176a11323721ef2720c9321413af41274fe..b53a439237735ad3c63b88a5183bcbf46f0789d8 100644
--- a/chrome/browser/chromeos/login/ui/login_display_host_impl.h
+++ b/chrome/browser/chromeos/login/ui/login_display_host_impl.h
@@ -33,6 +33,10 @@
 
 class PrefService;
 
+namespace browser_lifetime {
+class ScopedKeepAlive;
+}
+
 namespace content {
 class RenderFrameHost;
 class WebContents;
@@ -306,6 +310,9 @@ class LoginDisplayHostImpl : public LoginDisplayHost,
   // True is subscribed as keyboard controller observer.
   bool is_observing_keyboard_;
 
+  // Keeps the browser alife on the login/oobe screen.
+  scoped_ptr<browser_lifetime::ScopedKeepAlive> keep_alive_;
+
   // Keeps a copy of the old Drag'n'Drop client, so that it would be disabled
   // during a login session and restored afterwards.
   scoped_ptr<aura::client::ScopedDragDropDisabler> scoped_drag_drop_disabler_;