Use depot_tools module's methods or package_repo_resource function to
determine paths of tools that live in depot_tools

R=iannucci@chromium.org, martiniss@chromium.org
BUG=662586

Change-Id: Ic3172308c140f7f19e982ec6ec5a4b1b83261e1b
Reviewed-on: https://chromium-review.googlesource.com/411936Reviewed-by: Erik Staab <estaab@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Nodir Turakulov <nodir@chromium.org>