Make "source" a required argument of AppLaunchParams and fill in the argument in all call points.

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 a6bb71b74b4251c45c921a81c135f24c8bc420da..b95f598ce8ff0232f1bab13416711b47e5772e2a 100644
--- a/chrome/browser/background/background_mode_manager.cc
+++ b/chrome/browser/background/background_mode_manager.cc
@@ -32,6 +32,7 @@
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/chrome_pages.h"
+#include "chrome/browser/ui/extensions/app_launch_params.h"
 #include "chrome/browser/ui/extensions/application_launch.h"
 #include "chrome/browser/ui/host_desktop.h"
 #include "chrome/browser/ui/user_manager.h"
@@ -44,6 +45,7 @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/user_metrics.h"
 #include "extensions/browser/extension_system.h"
+#include "extensions/common/constants.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handlers/options_page_info.h"
 #include "extensions/common/permissions/permission_set.h"
@@ -318,7 +320,8 @@ void BackgroundModeManager::RegisterProfile(Profile* profile) {
 void BackgroundModeManager::LaunchBackgroundApplication(
     Profile* profile,
     const Extension* extension) {
-  OpenApplication(AppLaunchParams(profile, extension, NEW_FOREGROUND_TAB));
+  OpenApplication(AppLaunchParams(profile, extension, NEW_FOREGROUND_TAB,
+                                  extensions::SOURCE_BACKGROUND));
 }
 
 bool BackgroundModeManager::IsBackgroundModeActive() {