The link to https://google-styleguide.googlecode.com/svn/trunk/cppguide.xml is
no longer available. Point to GitHub instead.

Change-Id: I5a1010b42bd2e70348ae7ca6c5783d65520ff565
Reviewed-on: https://chromium-review.googlesource.com/488602Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>