Change extension icon load errors to warnings

chrome/test/data/extensions/api_test/browser_action/missing_icon/background.js

 // Copyright (c) 2011 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.
 
 var canvas = document.getElementById("canvas").getContext('2d').
     getImageData(0, 0, 19, 19);
 var canvasHD = document.getElementById("canvas").getContext('2d').
     getImageData(0, 0, 38, 38);
 
 var setIconParamQueue = [
@@ skipping 18 matching lines @@
   try {
     chrome.browserAction.setIcon(setIconParamQueue.shift(), function() {
       chrome.test.notifyPass();});
   } catch (error) {
     console.log(error.message);
     chrome.test.notifyFail(error.message);
   }
 });
 
 chrome.test.notifyPass();