Add ScopedKeepAlive to c/b/lifetime

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 694f91057a64f4952800d09b07290f16d32f8487..7d095d538ab6fa813d478d6740f16586904581db 100644
--- a/chrome/browser/background/background_mode_manager.cc
+++ b/chrome/browser/background/background_mode_manager.cc
@@ -278,10 +278,8 @@ BackgroundModeManager::BackgroundModeManager(
       status_icon_(NULL),
       context_menu_(NULL),
       in_background_mode_(false),
-      keep_alive_for_startup_(false),
       keep_alive_for_test_(false),
       background_mode_suspended_(false),
-      keeping_alive_(false),
       weak_factory_(this) {
   // We should never start up if there is no browser process or if we are
   // currently quitting.
@@ -311,8 +309,7 @@ BackgroundModeManager::BackgroundModeManager(
   // extensions, at which point we should either run in background mode (if
   // there are background apps) or exit if there are none.
   if (command_line.HasSwitch(switches::kNoStartupWindow)) {
-    keep_alive_for_startup_ = true;
-    chrome::IncrementKeepAliveCount();
+    keep_alive_for_startup_.reset(new ScopedKeepAlive("BackgroundForStartup"));
   } 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
@@ -675,14 +672,18 @@ void BackgroundModeManager::ExecuteCommand(int command_id, int event_flags) {
 
 ///////////////////////////////////////////////////////////////////////////////
 //  BackgroundModeManager, private
+void BackgroundModeManager::ReleaseStartupKeepAlive() {
+  keep_alive_for_startup_.reset();
+}
+
 void BackgroundModeManager::DecrementKeepAliveCountForStartup() {
   if (keep_alive_for_startup_) {
-    keep_alive_for_startup_ = false;
     // We call this via the message queue to make sure we don't try to end
     // 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(&BackgroundModeManager::ReleaseStartupKeepAlive,
+                              base::Unretained(this)));

[sky, 2016/02/19 21:02:49]

How do you know the unretained is safe here?

[dgn, 2016/02/22 18:01:19]

It's covered by the keep_alive_for_startup_ check, which keeps the browser alive
and because BackgroundModeManager is owned by browser_process, it will stay
around until browser_process shuts down, which is caused by removing keep
alives. I'll add a comment to say that.

   }
 }
 
@@ -761,19 +762,14 @@ void BackgroundModeManager::ResumeBackgroundMode() {
 
 void BackgroundModeManager::UpdateKeepAliveAndTrayIcon() {
   if (in_background_mode_ && !background_mode_suspended_) {
-    if (!keeping_alive_) {
-      keeping_alive_ = true;
-      chrome::IncrementKeepAliveCount();
-    }
+    if (!keep_alive_)
+      keep_alive_.reset(new ScopedKeepAlive("Background"));
     CreateStatusTrayIcon();
     return;
   }
 
   RemoveStatusTrayIcon();
-  if (keeping_alive_) {
-    keeping_alive_ = false;
-    chrome::DecrementKeepAliveCount();
-  }
+  keep_alive_.reset();
 }
 
 void BackgroundModeManager::OnBrowserAdded(Browser* browser) {