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

chrome/browser/background/background_mode_manager.cc

Index: chrome/browser/background/background_mode_manager.cc
diff --git a/chrome/browser/background/background_mode_manager.cc b/chrome/browser/background/background_mode_manager.cc
index 5bd2c6c5fa8186d2801aa1bd30ec1263283e66fd..df6a1aada17ca85ff67348a769b2d80483aaf1f8 100644
--- a/chrome/browser/background/background_mode_manager.cc
+++ b/chrome/browser/background/background_mode_manager.cc
@@ -28,6 +28,7 @@
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/extension_service.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/profiles/profile_info_cache.h"
 #include "chrome/browser/profiles/profile_manager.h"
@@ -343,7 +344,7 @@ BackgroundModeManager::BackgroundModeManager(
   // there are background apps) or exit if there are none.
   if (command_line.HasSwitch(switches::kNoStartupWindow)) {
     keep_alive_for_startup_ = true;
-    chrome::IncrementKeepAliveCount();
+    browser_lifetime::IncrementKeepAliveCount();
   } else {
     // Otherwise, start with background mode suspended in case we're launching
     // in a mode that doesn't open a browser window. It will be resumed when the
@@ -680,7 +681,7 @@ void BackgroundModeManager::ExecuteCommand(int command_id, int event_flags) {
       // Background mode must already be enabled (as otherwise this menu would
       // not be visible).
       DCHECK(IsBackgroundModePrefEnabled());
-      DCHECK(chrome::WillKeepAlive());
+      DCHECK(browser_lifetime::WillKeepAlive());
 
       RecordMenuItemClick(MENU_ITEM_KEEP_RUNNING);
 
@@ -713,7 +714,7 @@ void BackgroundModeManager::DecrementKeepAliveCountForStartup() {
     // keep-alive (which can shutdown Chrome) before the message loop has
     // started.
     base::ThreadTaskRunnerHandle::Get()->PostTask(
-        FROM_HERE, base::Bind(&chrome::DecrementKeepAliveCount));
+        FROM_HERE, base::Bind(&browser_lifetime::DecrementKeepAliveCount));
   }
 }
 
@@ -794,7 +795,7 @@ void BackgroundModeManager::UpdateKeepAliveAndTrayIcon() {
   if (in_background_mode_ && !background_mode_suspended_) {
     if (!keeping_alive_) {
       keeping_alive_ = true;
-      chrome::IncrementKeepAliveCount();
+      browser_lifetime::IncrementKeepAliveCount();
 
 #if defined(OS_WIN)
       browser_watcher::ExitFunnel::RecordSingleEvent(
@@ -808,7 +809,7 @@ void BackgroundModeManager::UpdateKeepAliveAndTrayIcon() {
   RemoveStatusTrayIcon();
   if (keeping_alive_) {
     keeping_alive_ = false;
-    chrome::DecrementKeepAliveCount();
+    browser_lifetime::DecrementKeepAliveCount();
 
 #if defined(OS_WIN)
     browser_watcher::ExitFunnel::RecordSingleEvent(
@@ -867,7 +868,7 @@ int BackgroundModeManager::GetBackgroundClientCount() const {
   // clients.
   for (const auto& it : background_mode_data_)
     count += it.second->GetBackgroundClientCount();
-  DCHECK(count >= 0);
+  DCHECK_GE(count, 0);
   return count;
 }