power_LoadTest: Add parameter for custom tasks

client/site_tests/power_LoadTest/extension/testparams.js

 // Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // External Test Parameters Content Script!
 
 // initial values.
 var test_time_ms = 0;
 var should_scroll = false;
 var should_scroll_up = false;
 var scroll_loop = false;
 var scroll_interval_ms = 0;
 var scroll_by_pixels = 0;
+var tasks = "";
 
 document.getElementById('myCustomEventDiv').addEventListener('myCustomEvent',
   function() {
     // pull our test parameters from divs on this page.
     var eventData = document.getElementById('myCustomEventDiv').innerText;
     test_time_ms = document.getElementById('test_time_ms').innerText;
     should_scroll = document.getElementById('should_scroll').innerText;
     should_scroll_up = document.getElementById('should_scroll_up').innerText;
     scroll_loop = document.getElementById('scroll_loop').innerText;
     scroll_interval_ms = document.getElementById('scroll_interval_ms').innerText;
     scroll_by_pixels = document.getElementById('scroll_by_pixels').innerText;
+    tasks = document.getElementById('tasks').innerText;
 
     // pass to background page via sendRequest.
     var request = { _test_time_ms : test_time_ms,
                     _should_scroll : should_scroll,
                     _should_scroll_up : should_scroll_up,
                     _scroll_loop : scroll_loop,
                     _scroll_interval_ms : scroll_interval_ms,
-                    _scroll_by_pixels : scroll_by_pixels
+                    _scroll_by_pixels : scroll_by_pixels,
+                    _tasks : tasks
                   }
     chrome.extension.sendRequest(request);
   }
 );