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

extensions/renderer/resources/app_runtime_custom_bindings.js

 // Copyright 2014 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.
 
 // Custom binding for the chrome.app.runtime API.
 
 var binding = require('binding').Binding.create('app.runtime');
 
 var AppViewGuestInternal =
     require('binding').Binding.create('appViewGuestInternal').generate();
@@ skipping 29 matching lines @@
     // An onLaunched corresponding to file_handlers in the app's manifest.
     var items = [];
     var numItems = launchData.items.length;
     var itemLoaded = function(err, item) {
       if (err) {
         console.error('Error getting fileEntry, code: ' + err.code);
       } else {
         $Array.push(items, item);
       }
       if (--numItems === 0) {
-        var data = { isKioskSession: launchData.isKioskSession };
+        var data = {
+          isKioskSession: launchData.isKioskSession,
+          source: launchData.source
+        };
         if (items.length !== 0) {
           data.id = launchData.id;
           data.items = items;
         }
         dispatch([data]);
       }
     };
     $Array.forEach(launchData.items, function(item) {
       var fs = GetIsolatedFileSystem(item.fileSystemId);
       fs.root.getFile(item.baseName, {}, function(fileEntry) {
         entryIdManager.registerEntry(item.entryId, fileEntry);
         itemLoaded(null, { entry: fileEntry, type: item.mimeType });
       }, function(fileError) {
         itemLoaded(fileError);
       });
     });
   } else {
     // Default case. This currently covers an onLaunched corresponding to
     // url_handlers in the app's manifest.
     dispatch([launchData]);
   }
 });
 
 exports.binding = binding.generate();