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

chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc

Index: chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
index 0d81c8f1cf93e121b3ce7674c40e9a4df2421175..611cc90eee78947864f33efe703875e96927d301 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
@@ -56,6 +56,7 @@
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_tabstrip.h"
 #include "chrome/browser/ui/browser_window.h"
+#include "chrome/browser/ui/extensions/app_launch_params.h"
 #include "chrome/browser/ui/extensions/application_launch.h"
 #include "chrome/browser/ui/extensions/extension_enable_flow.h"
 #include "chrome/browser/ui/host_desktop.h"
@@ -734,10 +735,9 @@ void ChromeLauncherController::LaunchApp(const std::string& app_id,
 #endif
 
   // The app will be created for the currently active profile.
-  AppLaunchParams params(profile_,
-                         extension,
-                         event_flags,
-                         chrome::HOST_DESKTOP_TYPE_ASH);
+  AppLaunchParams params(profile_, extension, event_flags,
+                         chrome::HOST_DESKTOP_TYPE_ASH,
+                         extensions::SOURCE_APP_LAUNCHER);
   if (source != ash::LAUNCH_FROM_UNKNOWN &&
       app_id == extensions::kWebStoreAppId) {
     // Get the corresponding source string.
@@ -749,10 +749,6 @@ void ChromeLauncherController::LaunchApp(const std::string& app_id,
         extension_url, extension_urls::kWebstoreSourceField, source_value);
   }
 
-  params.source = (source == ash::LAUNCH_FROM_UNKNOWN)
-                      ? extensions::SOURCE_UNTRACKED
-                      : extensions::SOURCE_APP_LAUNCHER;
-
   OpenApplication(params);
 }