Add a new field "source" in launchData of chrome.app.runtime.onLaunched() to trace launch source.

chrome/browser/ui/extensions/application_launch.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/extensions/application_launch.h"
 
 #include <string>
 
 #include "apps/launcher.h"
 #include "base/metrics/histogram.h"
@@ skipping 134 matching lines @@
 
   UMA_HISTOGRAM_ENUMERATION(
       "Extensions.AppLaunchContainer", params.container, 100);
 
   if (CanLaunchViaEvent(extension)) {
     // Remember what desktop the launch happened on so that when the app opens a
     // window we can open them on the right desktop.
     PerAppSettingsServiceFactory::GetForBrowserContext(profile)->
         SetDesktopLastLaunchedFrom(extension->id(), params.desktop_type);
 
-    apps::LaunchPlatformAppWithCommandLine(
-        profile, extension, params.command_line, params.current_directory);
+    apps::LaunchPlatformAppWithCommandLine(profile,
+                                           extension,
+                                           params.command_line,
+                                           params.current_directory,
+                                           params.source);
     return NULL;
   }
 
   // Record v1 app launch. Platform app launch is recorded when dispatching
   // the onLaunched event.
   prefs->SetLastLaunchTime(extension->id(), base::Time::Now());
 
   GURL url = UrlForExtension(extension, params.override_url);
   switch (params.container) {
     case extensions::LAUNCH_CONTAINER_NONE: {
@@ skipping 66 matching lines @@
 
   return tab;
 }
 
 bool CanLaunchViaEvent(const extensions::Extension* extension) {
   const extensions::FeatureProvider* feature_provider =
       extensions::FeatureProvider::GetAPIFeatures();
   extensions::Feature* feature = feature_provider->GetFeature("app.runtime");
   return feature->IsAvailableToExtension(extension).is_available();
 }