Improve WebstoreInstaller error handling.

chrome/test/data/extensions/api_test/webstore_private/install_bundle_invalid.html

 <!--
  * 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.
 -->
 <script src="common.js"></script>
 <script>
 
 var bundleItems = [
   {
     id: 'begfmnajjkbjdgmffnjaojchoncnmngg',
     manifest: getManifest('bundle/app1.json'),
     localizedName: 'app.1'
   },
   {
     id: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa',  // Invalid CRX.
     manifest: getManifest('bundle/app2.json'),
     localizedName: 'app.2'
   },
   {
     id: 'bmfoocgfinpmkmlbjhcbofejhkhlbchk',  // Wrong manifest.
     manifest: getManifest('bundle/extension2.json'),
     localizedName: 'extension.1'
   },
   {
-    id: 'pkapffpjmiilhlhbibjhamlmdhfneidj',
+    id: 'pkapffpjmiilhlhbibjhamlmdhfneidj',  // No CRX, 404.
     manifest: getManifest('bundle/extension2.json'),
     localizedName: 'extension.2'
   }
 ];
 
 var installed = [
-  'begfmnajjkbjdgmffnjaojchoncnmngg',
-  'pkapffpjmiilhlhbibjhamlmdhfneidj'
+  'begfmnajjkbjdgmffnjaojchoncnmngg'
 ];
 
 var failed = [
   'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa',
-  'bmfoocgfinpmkmlbjhcbofejhkhlbchk'
+  'bmfoocgfinpmkmlbjhcbofejhkhlbchk',
+  'pkapffpjmiilhlhbibjhamlmdhfneidj'
 ];
 
 runTests([
   function successfulInstall() {
     chrome.webstorePrivate.installBundle(
         bundleItems, callbackPass(function() {
       installed.forEach(function(id) {
         checkItemInstalled(
             id,
             callbackPass(function(result) { assertTrue(result); }));
@@ skipping 14 matching lines @@
            callbackPass(function(result) { assertFalse(result); }));
     }));
   },
 
   function noItems() {
     chrome.webstorePrivate.installBundle([], callbackFail("unknown_error"));
   }
 ]);
 
 </script>