Add KeepAliveStateObserver, add the Restart option

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 b219e831d9b66ce6977c0c6b73964aaf6214bbe7..45a89f2b8d30bd0cce08db671c3f1cbe5d0df35f 100644
--- a/chrome/browser/background/background_mode_manager.cc
+++ b/chrome/browser/background/background_mode_manager.cc
@@ -311,7 +311,8 @@ BackgroundModeManager::BackgroundModeManager(
   // there are background apps) or exit if there are none.
   if (command_line.HasSwitch(switches::kNoStartupWindow)) {
     keep_alive_for_startup_.reset(
-        new ScopedKeepAlive(keep_alive::Origin::BACKGROUND_MODE_MANAGER));
+        new ScopedKeepAlive(keep_alive::Origin::BACKGROUND_MODE_MANAGER_STARTUP,

[Bernhard Bauer, 2016/02/24 16:54:33]

Are we ever going to use the same origin with different restart options? If not,
it seems kind of strange to centralize origins themselves but keep the restart
options at the call sites. Maybe something to bring up  with Scott over on the
other CL?

[dgn, 2016/02/24 19:08:32]

Up to callers to decide what to do with their origins I guess? My interpretation
is that since we don't have strings to declare and risk typos, spreading enums
is less of an issue. So in a sense it's more consistent with the changes Scott
had me make.

+                            keep_alive::RestartOption::DISABLED));
   } 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
@@ -765,10 +766,10 @@ void BackgroundModeManager::ResumeBackgroundMode() {
 
 void BackgroundModeManager::UpdateKeepAliveAndTrayIcon() {
   if (in_background_mode_ && !background_mode_suspended_) {
-    if (!keep_alive_) {
+    if (!keep_alive_)

[Bernhard Bauer, 2016/02/24 16:54:33]

Keep the braces, as the body is more than one line.

       keep_alive_.reset(
-          new ScopedKeepAlive(keep_alive::Origin::BACKGROUND_MODE_MANAGER));
-    }
+          new ScopedKeepAlive(keep_alive::Origin::BACKGROUND_MODE_MANAGER,
+                              keep_alive::RestartOption::ENABLED));
     CreateStatusTrayIcon();
     return;
   }