GitLab

This prepares for a pending commit to the internal chrome_cleaner repo
which will delete the internal copy of import_util.py:

* Add separate GetChromiumRootDirectory and GetInternalRootDirectory
functions to clarify the ambiguous term "root directory" when called
from the internal repo mounted at //chrome/chrome_cleaner/internal.

* Move all the functions that depend on being called from inside the
chromium source tree to a separate import_paths.py script. (All the
current callers of these functions happen to be in
//chrome/chrome_cleaner/internal.)

* Delete code to find a local copy of find_depot_tools. It's no longer
supported to run this script without calling gclient sync, which will
update depot_tools.

R=proberge

Bug: 1004848
Change-Id: I829851f332975c950f1dcde59735ee96f34f295e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2451810Reviewed-by: proberge <proberge@chromium.org>
Commit-Queue: proberge <proberge@chromium.org>
Auto-Submit: Joe Mason <joenotcharles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814390}