Move shared file type images into chrome://theme/ scheme

chrome/browser/resources/file_manager/manifest.json

 {
   // chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/
   "key": "MIGdMA0GCSqGSIb3DQEBAQUAA4GLADCBhwKBgQDlhpGghtnNJ7pluQN0RDwbUxwwi99oM35ZEaFYvxPLrf0fIEC18cfDdJi6u4aJ+UoSpgzK731L0P/k4LvK2Rz9kVKOy0+IvuRrWkT7lbrLfA1UEBh02OA1AAshjmyRg4IxCqgl8ia8XWq6HKegS1y1KXZYGgb4qp7Bh9VC4cIzswIBIw==",
   "name": "Files",
   "version": "0.1",
   "description": "File Manager",
   "incognito" : "split",
   "icons": {
     "16": "images/icon16.png",
     "128": "images/icon128.png"
   },
   "permissions": [
     "fileBrowserHandler",
     "fileBrowserPrivate",
     "mediaPlayerPrivate",
     "metricsPrivate",
     "unlimitedStorage",
     "chrome://extension-icon/",
     "chrome://resources/",
+    "chrome://theme/",
     "tabs",
     "clipboardWrite",
     "clipboardRead",
     "https://*.googleusercontent.com/"
   ],
-  "content_security_policy": "default-src 'none'; script-src 'self'; style-src 'self' 'unsafe-inline'; frame-src 'self' about:; img-src 'self' chrome://resources data: https://docs.google.com https://*.googleusercontent.com chrome://extension-icon; media-src 'self' https://*.googleusercontent.com;",
+  "content_security_policy": "default-src 'none'; script-src 'self'; style-src 'self' 'unsafe-inline'; 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;",
   "app": {
     "launch": {
       "container": "panel",
       "local_path": "main.html"
     }
   },
   "file_browser_handlers": [
     {
       "id": "play",
       "default_title": "__MSG_PLAY_MEDIA__",
@@ skipping 136 matching lines @@
     "files": "main.html"
   },
   "background": {
     "transient": true,
     "persistent": false,
     "scripts": ["js/file_copy_manager.js",
                 "js/path_util.js",
                 "js/util.js"]
   }
 }