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This is part of a series of CLs redesigning the Badging API based on
TPAC feedback:
https://github.com/WICG/badging/issues/55

In a followup CL, the scope member will no longer be exposed to the
web:
https://chromium-review.googlesource.com/c/chromium/src/+/1816002

Note: The scope parameter was ignored in a previous CL, which is
why there are no unit/browser test changes.

Bug: 1006665
Change-Id: I176dfc28abaf661aaeaa1622e059c2b8cc851e12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1818892
Commit-Queue: Jay Harris <harrisjay@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701015}