Revert "Remove old AppRTC download location."

This reverts commit 5178cd4bbde856a9a168f08a89469f64b7b4494c.

Reason for revert: https://chromium-review.googlesource.com/c/chromium/src/+/1781684 is not landed yet!

Change-Id: Ia5feb218e928a1f7f4ca24f6fb3da380880e26f1
Reviewed-on: https://webrtc-review.googlesource.com/c/webrtc.DEPS/+/151360
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>