GitLab

Add feature flag MyFilesVolume that when it's enabled the MyFiles folder
will be an actual volume and Downloads will be just a plain folder
inside it.

Change GetDownloadsFolderForProfile to return
<cryptohome>/MyFiles/Downloads when the flag is active.

Add a new function GetMyFilesFolderForProfile which returns the correct
folder to be used as volume root, when the flag is disable it returns
the current value, by calling GetDownloadsFolderForProfile, which
returns <cryptohome>/Downloads. When the flag is active it returns
<cryptohome>/MyFiles.

Change GetPathDisplayTextForSettings to recognize the
<cryptohome>/MyFiles/Downloads pattern, for now it will return just
Downloads.

This is an initial work, follow up CLs wil change the rest of code base
to use either GetDownloadsFolderForProfile (when the code wants the
actual downloads folder) or GetMyFilesFolderForProfile when the code
wants the volume root, previously these 2 situations were the same path;
when the new flag is enabled they're different and depending on the use
case we might have to change to GetMyFilesFolderForProfile.

Bug: 873539

Change-Id: I7d01bc5370072ba574a6761d4a54d43d4b62ff6e
Reviewed-on: https://chromium-review.googlesource.com/c/1298824
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602979}