Camera: Add hidden experimental tearDown method.

Bug: 18949148
Change-Id: Ie86ec7d1ec3db54e1154563b2339a208a935f849
diff --git a/services/camera/libcameraservice/api2/CameraDeviceClient.h b/services/camera/libcameraservice/api2/CameraDeviceClient.h
index 0f485ca..1f8b39d 100644
--- a/services/camera/libcameraservice/api2/CameraDeviceClient.h
+++ b/services/camera/libcameraservice/api2/CameraDeviceClient.h
@@ -111,6 +111,9 @@
     // Prepare stream by preallocating its buffers
     virtual status_t      prepare(int streamId);
 
+    // Tear down stream resources by freeing its unused buffers
+    virtual status_t      tearDown(int streamId);
+
     /**
      * Interface used by CameraService
      */