focus_mode: Parse `playbackReportingToken` from queue.prepare/queue.next requests

This parses `playbackReportingToken` from queue.prepare/queue.next
requests so that the player can report the playback when needed later.

Bug: b/348698192
Test: Manual
Change-Id: I50f1b9662d6a6661f16b4dd5d75826aae385a2a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5646176
Reviewed-by: Richard Chui <richui@chromium.org>
Commit-Queue: Yongshun Liu <yongshun@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1319213}
NOKEYCHECK=True
GitOrigin-RevId: bf768f460da7edb58450fab204aa89b6899f8711
2 files changed