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

chrome/browser/ui/browser.cc

Index: chrome/browser/ui/browser.cc
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index 24e66d5bc5b64fc37c86952cf422503a53cf3898..169d0f61b6edfa2783f6878dd586317621629409 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -61,6 +61,7 @@
 #include "chrome/browser/history/top_sites_factory.h"
 #include "chrome/browser/infobars/infobar_service.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
+#include "chrome/browser/lifetime/browser_keep_alive.h"
 #include "chrome/browser/memory/tab_discard_state.h"
 #include "chrome/browser/notifications/notification_ui_manager.h"
 #include "chrome/browser/pepper_broker_infobar_delegate.h"
@@ -711,7 +712,7 @@ void Browser::OnWindowClosing() {
   // AppController on the Mac, or BackgroundContentsService for background
   // pages).
   bool should_quit_if_last_browser =
-      browser_shutdown::IsTryingToQuit() || !chrome::WillKeepAlive();
+      browser_shutdown::IsTryingToQuit() || !browser_lifetime::WillKeepAlive();
 
   if (should_quit_if_last_browser && chrome::ShouldStartShutdown(this))
     browser_shutdown::OnShutdownStarting(browser_shutdown::WINDOW_CLOSE);