Add experimental camera session prepare API.

Bug: 18949148
Change-Id: I8f73e68ea2e3acc60d98954106f364d13f439a82
diff --git a/services/camera/libcameraservice/device2/Camera2Device.h b/services/camera/libcameraservice/device2/Camera2Device.h
index 34c1ded..b4d343c 100644
--- a/services/camera/libcameraservice/device2/Camera2Device.h
+++ b/services/camera/libcameraservice/device2/Camera2Device.h
@@ -88,6 +88,7 @@
     // Prepare and tearDown are no-ops
     virtual status_t prepare(int streamId);
     virtual status_t tearDown(int streamId);
+    virtual status_t prepare(int maxCount, int streamId);
 
     virtual uint32_t getDeviceVersion();
     virtual ssize_t getJpegBufferSize(uint32_t width, uint32_t height) const;