This reverts commit 3e6d7c1c.

Reason for revert: maybe caused outage.

Original change's description:
> gclient: remove support for $matching_files in hooks
> 
> This feature seems to be unused, and removing it will
> simplify handling hooks a little bit.
> 
> Bug: 661382
> Change-Id: I89f28dedb7f59cd475b176cfb1f023094520d6b7
> Reviewed-on: https://chromium-review.googlesource.com/509614
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Commit-Queue: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
> 

TBR=phajdan.jr@chromium.org,dpranke@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
Bug: 661382

Change-Id: I47fe26e7381682b5b428a3775bf27a551c57d5e6
Reviewed-on: https://chromium-review.googlesource.com/512344Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>