Fix unreleased TtsVoice

Replace pointer with instance.

BUG=None
TEST=gmerge speech_synthesis

Change-Id: Iacba7ae227b7638baa9dec53d9b79e251f94b695
Reviewed-on: https://gerrit.chromium.org/gerrit/13785
Commit-Ready: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Tested-by: Ryo Hashimoto <hashimoto@chromium.org>
7 files changed