Files.app: Remove support for chrome://files.

chrome/browser/resources/file_manager/manifest.json

 {
   // chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/
   "key": "MIGdMA0GCSqGSIb3DQEBAQUAA4GLADCBhwKBgQDlhpGghtnNJ7pluQN0RDwbUxwwi99oM35ZEaFYvxPLrf0fIEC18cfDdJi6u4aJ+UoSpgzK731L0P/k4LvK2Rz9kVKOy0+IvuRrWkT7lbrLfA1UEBh02OA1AAshjmyRg4IxCqgl8ia8XWq6HKegS1y1KXZYGgb4qp7Bh9VC4cIzswIBIw==",
   "manifest_version": 2,
   "name": "Files",
   "version": "3.0",
   "description": "File Manager",
   "incognito" : "split",
   "icons": {
     "16": "images/icon16.png",
@@ skipping 195 matching lines @@
       "file_filters": []
     },
     // Opens the passed directory after launching Files.app.
     {
       "id": "open",
       "default_title": "__MSG_OPEN_ACTION__",
       "default_icon": "images/filetype_generic.png",
       "file_filters": []
     }
   ],
-  "chrome_url_overrides": {
-    "files": "main.html"
-  },
   // Required to import scripts in a web worker. Note, that in Apps v2, it is
   // enough that anything is passed to web_accessible_resources. If there is
   // at least any file, then all files are allowed. http://crbug.com/179127.
   "web_accessible_resources": ["js/metadata/byte_reader.js"],
   "app": {
     "background": {
       "scripts": [
         "chrome://resources/js/load_time_data.js",
         "chrome://resources/js/cr.js",
         "chrome://resources/js/cr/event_target.js",
         "chrome://resources/js/cr/ui/array_data_model.js",
         "js/util.js",
         "js/path_util.js",
         "js/async_util.js",
         "js/volume_manager.js",
         "js/file_operation_manager.js",
         "js/test_util.js",
         "js/progress_center_common.js",
         "js/progress_center.js",
         "js/background.js"]
     },
     // chrome-extension://pmfjbimdmchhbnneeidfognadeopoehp is the image loader extension.
     "content_security_policy": "default-src 'none'; script-src 'self' chrome://resources chrome-extension://pmfjbimdmchhbnneeidfognadeopoehp; style-src 'self' 'unsafe-inline' chrome://resources; frame-src 'self' about:; img-src 'self' chrome://resources chrome://theme data: https://docs.google.com https://*.googleusercontent.com chrome://extension-icon; media-src 'self' https://*.googleusercontent.com; connect-src https://drive.google.com; object-src 'self'"
   }
 }