Description of icons:
- infobar_protected_media_identifier.png: Blue icon used on the actual
  permission prompt.
- permission_protected_media.png: Gray icon used on site settings.

Optimized with:
  tools/resources/optimize-png-files.sh -o2 -c HEAD~ -v

For historical context, previously those icons were added in
https://codereview.chromium.org/2123533002

For Protected Content icon change on desktop platforms, see
https://chromium-review.googlesource.com/c/chromium/src/+/1003146

Bug: 454980
Test: Manually tried it and verified on https://permission.site
Change-Id: Idc74992632161ee19944146395ac87d79adee848
Reviewed-on: https://chromium-review.googlesource.com/996754
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549559}