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

chrome/browser/ui/panels/panel.cc

Index: chrome/browser/ui/panels/panel.cc
diff --git a/chrome/browser/ui/panels/panel.cc b/chrome/browser/ui/panels/panel.cc
index 56618ba689a3b5aaf4687bd3d216f4bfd6cc4881..95ebe0a896069021e4e9bc9aea787f683c1c5941 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -18,6 +18,7 @@
 #include "chrome/browser/extensions/window_controller.h"
 #include "chrome/browser/extensions/window_controller_list.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
+#include "chrome/browser/lifetime/browser_keep_alive.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_tab_helper.h"
 #include "chrome/browser/task_management/web_contents_tags.h"
@@ -160,7 +161,7 @@ Panel::~Panel() {
   DCHECK(!collection_);
 #if !defined(USE_AURA)
   // Invoked by native panel destructor. Do not access native_panel_ here.
-  chrome::DecrementKeepAliveCount();  // Remove shutdown prevention.
+  browser_lifetime::DecrementKeepAliveCount();  // Remove shutdown prevention.
 #endif
 }
 
@@ -552,7 +553,7 @@ void Panel::Initialize(const GURL& url,
 #if !defined(USE_AURA)
   // Keep alive for AURA has been moved to panel_view.
   // Prevent the browser process from shutting down while this window is open.
-  chrome::IncrementKeepAliveCount();
+  browser_lifetime::IncrementKeepAliveCount();
 #endif
 
   UpdateAppIcon();