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This cl does the following:
- change html encoding to utf-8 to support translation files.
- add build-time grd file selection.
- build real resources (if src-internal is available) or mock resources (for tests/if
src-internal is unavailable).
- iterate over chromeos_media_app_bundle_resources to add them as resources to serve at runtime.

Submit after landing cl/277647372 & pushing to src-internal.

Design doc: go/cr-g3-remote-resources#bookmark=id.b1xx7d4iasyv

Bug: 996088, 1023739, b/141645032, b/142915800
Change-Id: Ib26a65b84f61b1f938e22c4242114448111c3469
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1895263Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: David Lei <dlei@google.com>
Cr-Commit-Position: refs/heads/master@{#714846}