[Media Image] Remove artwork from metadata

Remove artwork from metadata as we have moved it
to a separate observer method. On Android we add
a mediaSessionArtworkChanged that is called
when the artwork is changed.


Change-Id: I90426c30f6ba1fcb61bd5af56819e16bd64fddc8
Reviewed-on: https://chromium-review.googlesource.com/c/1453104
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Tommy Steimel <steimel@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631817}
21 files changed