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This CL implements the option F in [1].
Add Material-like theme as a platform-matching theme.

[1] https://github.com/tkent-google/std-switch/issues/6#issuecomment-499842423

Bug: 972476
Change-Id: I643d36b0a4750191d45e7e6cfe2ae320826e3f48
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832128
Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701952}