Adds support for setting numeric badges on Windows and OSX.

Spec Draft: https://wicg.github.io/badging/

In previous CLs, support for setting "•" badge
was added. This CL updates the mojo interface
to pass an optional numeric value through from the
render process to display on the badge (falling
back to the "•" when no number is specified).

Notes
- Negative numbers are not supported
- Setting the badge to '0' will clear the badge
- Numeric badges are saturated to '99+' for
numbers greater than 99, as we only have 16x16px
in which to draw on Windows.

Bug: 719176
Change-Id: I470f28e770ed4a5db29d0e61c86da3e7fd152acc
Reviewed-on: https://chromium-review.googlesource.com/c/1358102
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Commit-Queue: Jay Harris <harrisjay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618040}
16 files changed