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

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

Index: chrome/browser/chromeos/login/ui/login_display_host_impl.cc
diff --git a/chrome/browser/chromeos/login/ui/login_display_host_impl.cc b/chrome/browser/chromeos/login/ui/login_display_host_impl.cc
index f3d283e9076129a5e4c7e65951365ef35b6a9793..6a0fdd387e857f945b644e236f1b2c8e571a2629 100644
--- a/chrome/browser/chromeos/login/ui/login_display_host_impl.cc
+++ b/chrome/browser/chromeos/login/ui/login_display_host_impl.cc
@@ -55,6 +55,7 @@
 #include "chrome/browser/chromeos/system/timezone_util.h"
 #include "chrome/browser/chromeos/ui/focus_ring_controller.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
+#include "chrome/browser/lifetime/browser_keep_alive.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/ui/webui/chromeos/login/oobe_ui.h"
 #include "chrome/common/chrome_constants.h"
@@ -307,7 +308,7 @@ LoginDisplayHostImpl::LoginDisplayHostImpl(const gfx::Rect& background_bounds)
   default_host_ = this;
 
   // Make sure chrome won't exit while we are at login/oobe screen.
-  chrome::IncrementKeepAliveCount();
+  browser_lifetime::IncrementKeepAliveCount();
 
   bool is_registered = StartupUtils::IsDeviceRegistered();
   bool zero_delay_enabled = WizardController::IsZeroDelayEnabled();
@@ -397,7 +398,7 @@ LoginDisplayHostImpl::~LoginDisplayHostImpl() {
   ResetLoginWindowAndView();
 
   // Let chrome process exit after login/oobe screen if needed.
-  chrome::DecrementKeepAliveCount();
+  browser_lifetime::DecrementKeepAliveCount();
 
   default_host_ = NULL;
   // TODO(tengs): This should be refactored. See crbug.com/314934.