Showing the promo on release channel only.

chrome/browser/resources/file_manager/js/file_manager.js

 // 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.
 
 /**
  * FileManager constructor.
  *
  * FileManager objects encapsulate the functionality of the file selector
  * dialogs, as well as the full screen file manager application (though the
  * latter is not yet implemented).
@@ skipping 3973 matching lines @@
 
   FileManager.prototype.showGDataWelcome_ = function(type) {
     if (this.dialogContainer_.getAttribute('gdrive-welcome') != type) {
       this.dialogContainer_.setAttribute('gdrive-welcome', type);
       this.requestResize_(200);  // Resize only after the animation is done.
     }
   };
 
   FileManager.prototype.createGDataWelcomeHandler_ = function() {
     var board = str('CHROMEOS_RELEASE_BOARD');
-    var new_welcome = board.match(/^(stumpy|lumpy)/i);
+    // It is 'canary' or 'beta' for the other channels.
+    var releaseChannel = str('BROWSER_VERSION_MODIFIER') == '';
+    var new_welcome = board.match(/^(stumpy|lumpy)/i) && releaseChannel;
 
     var WELCOME_HEADER_COUNTER_KEY = 'gdataWelcomeHeaderCounter';
     var WELCOME_HEADER_COUNTER_LIMIT = 5;
 
     function getHeaderCounter() {
       return parseInt(localStorage[WELCOME_HEADER_COUNTER_KEY] || '0');
     }
 
     if (getHeaderCounter() >= WELCOME_HEADER_COUNTER_LIMIT)
       return null;
@@ skipping 169 matching lines @@
     }
 
     var defaultActionSeparator =
         this.dialogDom_.querySelector('#default-action-separator');
 
     this.defaultActionMenuItem_.hidden = !taskItem;
     defaultActionSeparator.hidden = !taskItem;
   }
 })();