Need camera permission

```
11-24 16:19:54.603 18488-26881/com.example.android.mediarecorder E/AndroidRuntime: FATAL EXCEPTION: AsyncTask android/android-MediaRecorder#1
Process: com.example.android.mediarecorder, PID: 18488
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:318)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
at java.lang.Thread.run(Thread.java:762)
Caused by: java.lang.RuntimeException: Fail to connect to camera service
at android.hardware.Camera.(Camera.java:519)
at android.hardware.Camera.open(Camera.java:379)
at com.example.android.common.media.CameraHelper.getDefaultCameraInstance(CameraHelper.java:103)
at com.example.android.mediarecorder.MainActivity.prepareVideoRecorder(MainActivity.java:142)
at com.example.android.mediarecorder.MainActivity.access$000(MainActivity.java:44)
at com.example.android.mediarecorder.MainActivity$MediaPrepareTask.doInBackground(MainActivity.java:218)
at com.example.android.mediarecorder.MainActivity$MediaPrepareTask.doInBackground(MainActivity.java:213)
at android.os.AsyncTask$2.call(AsyncTask.java:304)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
at java.lang.Thread.run(Thread.java:762) 
```

Start with the stack trace entries in CameraHelper.java and MainActivity.java, especially Camera.open and prepareVideoRecorder. Check how camera permission is handled before the camera service is opened, then reproduce the crash on the affected Android setup. Done means the sample handles missing camera permission without the reported runtime exception.

Written by the indexing model from the issue text.