camera: Add AIDL interface for CameraServiceProxy.

- Adds an AIDL interface to allow the proxy camera service
  running in system server to accept RPCs from the camera
  service running in mediaserver.
- Request an update to the valid user set from the proxy
  camera service when mediaserver restarts to initialize
  properly + avoid DOS after a crash.

Bug: 21267484

Change-Id: Ib821582794ddd1e3574b5dc6c79f7cb197b57f10
diff --git a/services/camera/libcameraservice/CameraService.h b/services/camera/libcameraservice/CameraService.h
index 9b7163a..ce3cb44 100644
--- a/services/camera/libcameraservice/CameraService.h
+++ b/services/camera/libcameraservice/CameraService.h
@@ -702,6 +702,8 @@
 
     static String8 toString(std::set<userid_t> intSet);
 
+    static void pingCameraServiceProxy();
+
 };
 
 template<class Func>