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The previous wording about 'you can obtain the Windows SDK' made it
sound like this is a way to obtain the SDK, but it's really about how
to package up an existing installation.

Also do some other minor tweaks.

Bug: none
Change-Id: I1b835cdfe951c7b32ec71bc5dd8f249c9fec0b0d
Reviewed-on: https://chromium-review.googlesource.com/1113455
Commit-Queue: Hans Wennborg <hans@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570027}