[Fuchsia][EME] FuchsiaCdmFactory and ClearKey

Add FuchsiaCdmFactory which is used to create ContentDecryptionModule on
Fuchsia. Currently it only creates AesDecryptor for ClearKey.

Bug: 966191
Test: https://simpl.info/eme/clearkey/
Change-Id: I2787c5f44c2794987149975f7e9bc6d43dbe5cac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1643977
Reviewed-by: John Rummell <jrummell@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Yuchen Liu <yucliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678907}
5 files changed