Camera: Add hidden experimental tearDown method.

Bug: 18949148
Change-Id: Ie86ec7d1ec3db54e1154563b2339a208a935f849
diff --git a/services/camera/libcameraservice/common/CameraDeviceBase.h b/services/camera/libcameraservice/common/CameraDeviceBase.h
index 06177e3..cd25949 100644
--- a/services/camera/libcameraservice/common/CameraDeviceBase.h
+++ b/services/camera/libcameraservice/common/CameraDeviceBase.h
@@ -289,6 +289,11 @@
     virtual status_t prepare(int streamId) = 0;
 
     /**
+     * Free stream resources by dumping its unused gralloc buffers.
+     */
+    virtual status_t tearDown(int streamId) = 0;
+
+    /**
      * Get the HAL device version.
      */
     virtual uint32_t getDeviceVersion() = 0;