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

chrome/browser/ui/apps/chrome_app_delegate.cc

Index: chrome/browser/ui/apps/chrome_app_delegate.cc
diff --git a/chrome/browser/ui/apps/chrome_app_delegate.cc b/chrome/browser/ui/apps/chrome_app_delegate.cc
index 906cdeb6b0bf5d7e9c668cdb6b093c3573a9b353..b73f7b9139d6474c9d6277ffd0ea098ee3ba6ea6 100644
--- a/chrome/browser/ui/apps/chrome_app_delegate.cc
+++ b/chrome/browser/ui/apps/chrome_app_delegate.cc
@@ -7,11 +7,11 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/app_mode/app_mode_utils.h"
-#include "chrome/browser/apps/scoped_keep_alive.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/chrome_extension_web_contents_observer.h"
 #include "chrome/browser/favicon/favicon_utils.h"
 #include "chrome/browser/file_select_helper.h"
+#include "chrome/browser/lifetime/browser_keep_alive.h"
 #include "chrome/browser/media/media_capture_devices_dispatcher.h"
 #include "chrome/browser/platform_util.h"
 #include "chrome/browser/profiles/profile.h"
@@ -47,6 +47,8 @@
 #endif  // defined(ENABLE_PRINT_PREVIEW)
 #endif  // defined(ENABLE_PRINTING)
 
+using browser_lifetime::ScopedKeepAlive;
+
 namespace {
 
 // Time to wait for an app window to show before allowing Chrome to quit.