Fix bug where we were not displaying icons in the management

chrome/test/data/extensions/ui/create_extension_detail_value_expected_output/good-extension1.json

 {
   "id": "behllobkkfkfnphdnhnkndlbkcpglgmj",
   "version": "1.0.0.0",
   "name": "My extension 1",
   "enabled": true,
   "description": "The first extension that I made.",
   "permissions": ["http://*.google.com/*", "https://*.google.com/*"],
-  "icon": "icon_128.png",
   "order": 2,
   "content_scripts": [
     {
       "matches": ["file://*", "http://*.google.com/*", "https://*.google.com/*"],
       "js": ["script1.js", "script2.js"],
       "css": ["style1.css", "style2.css", "style2.css"]
     },
     {
       "matches": ["http://*.news.com/*"],
       "js": ["js_files/script3.js"]
     }
   ],
   "views": [
     {
       "path": "bar.html",
       "render_proess_id": 42,
       "render_view_id": 88
     },
     {
       "path": "dog.html",
       "render_proess_id": 0,
       "render_view_id": 0
     }
   ]
 }