Expose the "automatic downloads" content setting to extensions.

chrome/test/data/extensions/api_test/content_settings/standard/test.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.
 
 // Content settings API test
 // Run with browser_tests --gtest_filter=ExtensionApiTest.ContentSettings
 
 var cs = chrome.contentSettings;
 var default_content_settings = {
   "cookies": "session_only",
   "images": "allow",
   "javascript": "block",
   "plugins": "allow",
   "popups": "block",
   "location": "ask",
   "notifications": "ask",
   "fullscreen": "ask",
   "mouselock": "ask",
   "microphone": "ask",
   "camera": "ask",
   "unsandboxedPlugins": "ask",
+  "automaticDownloads": "ask"
 };
 
 var settings = {
   "cookies": "block",
   "images": "allow",
   "javascript": "block",
   "plugins": "block",
   "popups": "allow",
   "location": "block",
   "notifications": "block",
   "fullscreen": "allow",
   "mouselock": "block",
   "microphone": "block",
   "camera": "block",
   "unsandboxedPlugins": "block",
+  "automaticDownloads": "block"
 };
 
 Object.prototype.forEach = function(f) {
   var k;
   for (k in this) {
     if (this.hasOwnProperty(k))
       f(k, this[k]);
   }
 };
 
@@ skipping 48 matching lines @@
       'setting': 'block'
     }, chrome.test.callbackFail("Specific paths are not allowed."));
     cs.javascript.set({
       'primaryPattern': 'http://example.com/*',
       'secondaryPattern': 'file:///home/hansmoleman/*',
       'setting': 'allow'
     }, chrome.test.callbackFail(
         "Path wildcards in file URL patterns are not allowed."));
   }
 ]);