Reason for revert:
Breaks builds where use_udev==0 since certain targets just assume udev and never check against use_udev.
Udev package should be wrapped in a use_udev confitional altogether and all the locations using Udev should check against use_udev.
Original issue's description:
> Run pkg-config for Udev only if use_udev==1
>
> Some embedded platforms do not have udev support. The change will skip
> running pkg-config if use_udev=0.
>
> BUG=none
>
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=288770TBR=brettw@chromium.org
NOTRY=true
Review URL: https://codereview.chromium.org/469763002
git-svn-id: http://src.chromium.org/svn/trunk/src/build@289280 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
b1bf10e85f