[CCA] Cleanup for internal directory usage

Since we have removed the legacy migration logic in:
https://crrev.com/c/2407733, we don't need internal directory usage
anymore.

Note that we still need internal temporary directory to store
temporary video file for intent purpose.

Bug: 1127587
Test: Launch CCA and no error shows.
Change-Id: I2d2a09328f328a0e6c675f85145f215fd140c1b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2438082Reviewed-by: Shik Chen <shik@chromium.org>
Commit-Queue: Wei Lee <wtlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811997}

chromeos/components/camera_app_ui/resources/js/models/file_system.js

@@ -29,12 +29,6 @@ function hasImagePrefix(entry) {
   return entry.name.startsWith(IMAGE_PREFIX);
 }
 
-/**
- * Directory in the internal file system.
- * @type {?AbstractDirectoryEntry}
- */
-let internalDir = null;
-
 /**
  * Temporary directory in the internal file system.
  * @type {?AbstractDirectoryEntry}
@@ -55,18 +49,6 @@ export function getCameraDirectory() {
   return cameraDir;
 }
 
-/**
- * Initializes the directory in the internal file system.
- * @return {!Promise<!AbstractDirectoryEntry>} Promise for the directory result.
- */
-function initInternalDir() {
-  return new Promise((resolve, reject) => {
-    webkitRequestFileSystem(
-        window.PERSISTENT, 768 * 1024 * 1024 /* 768MB */,
-        (fs) => resolve(new ChromeDirectoryEntry(fs.root)), reject);
-  });
-}
-
 /**
  * Initializes the temporary directory in the internal file system.
  * @return {!Promise<!AbstractDirectoryEntry>} Promise for the directory result.
@@ -93,9 +75,6 @@ async function initCameraDirectory() {
  * @return {!Promise}
  */
 export async function initialize() {
-  internalDir = await initInternalDir();
-  assert(internalDir !== null);
-
   internalTempDir = await initInternalTempDir();
   assert(internalTempDir !== null);