Add matched_extensions field to PUPData and related mojo interface

Also includes a .clang_format file in the pup_data dir that was missed,
which caused dummy_signatures.cc to be reformatted.

R=csharp@chromium.org

Bug: 830892
Change-Id: I720c083ee6f8ee2b6f1805392419f43c91d43026
Reviewed-on: https://chromium-review.googlesource.com/c/1338205
Reviewed-by: Chris Sharp <csharp@chromium.org>
Commit-Queue: Joe Mason <joenotcharles@google.com>
Cr-Commit-Position: refs/heads/master@{#608806}
6 files changed