frameworks\base\services\core\java\com\android\server\pm\DefaultPermissionGrantPolicy.java
    先仿照已有的代码，给需要默认开权限的APP增加权限组：

    1.     /// START. Enable permissions during first boot. By ShawnXiaFei@20180927.
    2.     private static final Set<String> USAGE_PERMISSIONS = new ArraySet<>();
    3.     static {
    4.         //USAGE_PERMISSIONS.add(Manifest.permission.GET_TASKS);
    5.         USAGE_PERMISSIONS.add(Manifest.permission.PACKAGE_USAGE_STATS);
    6.         //USAGE_PERMISSIONS.add(Manifest.permission.REORDER_TASKS);
    7.     }
    8.     /// END. Enable permissions during first boot. By ShawnXiaFei@20180927.

    然后在 grantDefaultSystemHandlerPermissions 方法末尾处增加代码：
    （或搜索“Music”）

    1. private void grantDefaultSystemHandlerPermissions(int userId) {
    2.     Log.i(TAG, "Granting permissions to default platform handlers for user " + userId);
    4.     // 省略大量代码
    6.     synchronized (mService.mPackages) {
    7.         // Installer
    8.         PackageParser.Package installerPackage = getSystemPackageLPr(
    9.             mService.mRequiredInstallerPackage);
    10.         if (installerPackage != null
    11.             && doesPackageSupportRuntimePermissions(installerPackage)) {
    12.             grantRuntimePermissionsLPw(installerPackage, STORAGE_PERMISSIONS, true, userId);
    13.         }
    15.         // 省略大量代码
    17.         // Music
    18.         Intent musicIntent = new Intent(Intent.ACTION_VIEW);
    19.         musicIntent.addCategory(Intent.CATEGORY_DEFAULT);
    20.         musicIntent.setDataAndType(Uri.fromFile(new File("foo.mp3")),
    21.                                    AUDIO_MIME_TYPE);
    22.         PackageParser.Package musicPackage = getDefaultSystemHandlerActivityPackageLPr(
    23.             musicIntent, userId);
    24.         if (musicPackage != null
    25.             && doesPackageSupportRuntimePermissions(musicPackage)) {
    26.             grantRuntimePermissionsLPw(musicPackage, STORAGE_PERMISSIONS, userId);
    27.         }
    29.         /// START. Enable permissions during first boot. By ShawnXiaFei@20180927.
    30.         PackageParser.Package launcherPkg = getPackageLPr("com.rustybrick.kioskhome");
    31.         if(null != launcherPkg){
    32.             grantRuntimePermissionsLPw(launcherPkg, USAGE_PERMISSIONS, true, userId);
    33.             //grantRuntimePermissionsLPw(launcherPkg, STORAGE_PERMISSIONS, /*true,*/ userId);
    34.         }
    35.         /// END. Enable permissions during first boot. By ShawnXiaFei@20180927.
    37.         mService.mSettings.onDefaultRuntimePermissionsGrantedLPr(userId);
    38.     }
    39. }