Change ResponseCallback from interface to class

This CL changes the interface defined
in HandlerResponseCallback.java into class to avoid breaking
downstream in the future.

This CL is third of 5 CLs that handle error returned from isUVPAA
and avoid breaking downstream in the future.
First CL:
https://chromium-review.googlesource.com/c/chromium/src/+/1680996
Second CL:
https://chrome-internal-review.googlesource.com/c/clank/internal/apps/+/1426997

Bug: 976480
Change-Id: I3b536bd429547f29c52fb2cec21b4d0ea02e4c57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1679552
Commit-Queue: Suzy Li <suzyli@google.com>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Kim Paulhamus <kpaulhamus@chromium.org>
Cr-Commit-Position: refs/heads/master@{#674217}