Populate media transcripts without a media session

Currently a media session can end immediately when the video finishes
playing, but the user may still want to ask questions about the video,
so we should always include transcripts if they have been generated for
this render frame host. The other media data fields will be populated if
the video is playing or paused while the media session is still active.

Bug: 409427125
Change-Id: I102fc210dda3c8d86db1cca57246f5600ad121eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6851738
Reviewed-by: Khushal Sagar <khushalsagar@chromium.org>
Commit-Queue: Yiren Wang <yrw@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1503049}