GitLab

This CL enables PWA manifest updating to detect when sites update their
"icons" field (but not when the icon contents themselves change).

Screencast: https://bugs.chromium.org/p/chromium/issues/attachment?aid=423127&signed_aid=pWxFmMl1EjQvs_LiPg2zog==&inline=1

Bug: 926083
Change-Id: I6ff14e7b813c9526f8e423b4d3de50c7f5349abc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935297
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720855}