[Doc] Update instrumented_libraries.md

* Trusty->Xenial
* Avoid building as root
* Remove some hardcoded "thomasanderson" in paths

R=thestig

Bug: None
Change-Id: Ia05b5e5f7f590b07dbcfb18c1f864c57069200b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3209693
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#928973}

docs/linux/instrumented_libraries.md

@@ -9,27 +9,27 @@ others are optional, and are currently unused.
 ### Setting up a chroot
 
 Building the libraries requires `apt-get source`, so the build must be done from
-an Ubuntu 14.04 environment. The preferred way is using a chroot. To get
+an Ubuntu 16.04 environment. The preferred way is using a chroot. To get
 started, install `debootstrap` and `schroot`. If you're running a Debian-based
 distro, run:
 
 ```shell
 sudo apt install debootstrap schroot
 ```
 
-Create a configuration for a Trusty chroot:
+Create a configuration for a Xenial chroot:
 
 ```shell
-sudo $EDITOR /etc/schroot/chroot.d/trusty_amd64.conf
+sudo $EDITOR /etc/schroot/chroot.d/xenial_amd64.conf
 ```
 
 Add the following to the new file, replacing the instances of `thomasanderson`
 with your own username.
 
 ```
-[trusty_amd64]
-description=Ubuntu 14.04 Trusty for amd64
-directory=/srv/chroot/trusty_amd64
+[xenial_amd64]
+description=Ubuntu 16.04 Xenial for amd64
+directory=/srv/chroot/xenial_amd64
 personality=linux
 root-users=thomasanderson
 type=directory
@@ -39,8 +39,8 @@ users=thomasanderson
 Bootstrap the chroot:
 
 ```shell
-sudo mkdir -p /srv/chroot/trusty_amd64
-sudo debootstrap --variant=buildd --arch=amd64 trusty /srv/chroot/trusty_amd64 http://archive.ubuntu.com/ubuntu/
+sudo mkdir -p /srv/chroot/xenial_amd64
+sudo debootstrap --variant=buildd --arch=amd64 xenial /srv/chroot/xenial_amd64 http://archive.ubuntu.com/ubuntu/
 ```
 
 If your `$HOME` directory is not `/home` (as is the case on gLinux), then route
@@ -54,45 +54,45 @@ sudo mount --bind "$HOME" /home
 Add `sources.list`:
 
 ```shell
-sudo $EDITOR /srv/chroot/trusty_amd64/etc/apt/sources.list
+sudo $EDITOR /srv/chroot/xenial_amd64/etc/apt/sources.list
 ```
 
 Add the following contents to the file:
 
 ```
-deb     http://archive.ubuntu.com/ubuntu/ trusty          main restricted universe
-deb-src	http://archive.ubuntu.com/ubuntu/ trusty          main restricted universe
-deb     http://archive.ubuntu.com/ubuntu/ trusty-security main restricted universe
-deb-src http://archive.ubuntu.com/ubuntu/ trusty-security main restricted universe
-deb     http://archive.ubuntu.com/ubuntu/ trusty-updates  main restricted universe
-deb-src http://archive.ubuntu.com/ubuntu/ trusty-updates  main restricted universe
+deb     http://archive.ubuntu.com/ubuntu/ xenial          main restricted universe
+deb-src	http://archive.ubuntu.com/ubuntu/ xenial          main restricted universe
+deb     http://archive.ubuntu.com/ubuntu/ xenial-security main restricted universe
+deb-src http://archive.ubuntu.com/ubuntu/ xenial-security main restricted universe
+deb     http://archive.ubuntu.com/ubuntu/ xenial-updates  main restricted universe
+deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates  main restricted universe
 ```
 
 Enter the chroot and install the necessary packages:
 
 ```shell
-schroot -c trusty_amd64 -u root --directory /
+schroot -c xenial_amd64 -u root --directory /home/dev/chromium/src
 apt update
 apt install lsb-release sudo python pkg-config libgtk2.0-bin libdrm-dev nih-dbus-tool help2man
 ```
 
-Add `depot_tools` to your `PATH`. For example, I have it in `~/dev/depot_tools`,
-so I use:
+Install library packages:
 
 ```shell
-export PATH=/home/thomasanderson/dev/depot_tools/:$PATH
+third_party/instrumented_libraries/scripts/install-build-deps.sh
 ```
 
-Change to your src directory:
-
+Change to a non-root user:
 ```shell
-cd /home/thomasanderson/dev/chromium/src
+exit
+schroot -c xenial_amd64 -u `whoami` --directory /home/dev/chromium/src
 ```
 
-Install library packages:
+Add `depot_tools` to your `PATH`. For example, I have it in `~/dev/depot_tools`,
+so I use:
 
 ```shell
-third_party/instrumented_libraries/scripts/install-build-deps.sh
+export PATH=/home/dev/depot_tools/:$PATH
 ```
 
 Now we're ready to build the libraries. A clean build takes a little over 8
@@ -111,15 +111,12 @@ bucket. `dpranke@` can grant access.
 # Exit the chroot.
 exit
 
-# Fix permissions.
-sudo chown -R `whoami`:`groups | awk '{print $1;}'` *.tgz out/Instrumented-*
-
 # Move files into place.
 mv *.tgz third_party/instrumented_libraries/binaries
 
 # Upload.
-upload_to_google_storage.py -b chromium-instrumented-libraries third_party/instrumented_libraries/binaries/msan-chained-origins-trusty.tgz
-upload_to_google_storage.py -b chromium-instrumented-libraries third_party/instrumented_libraries/binaries/msan-no-origins-trusty.tgz
+upload_to_google_storage.py -b chromium-instrumented-libraries third_party/instrumented_libraries/binaries/msan-chained-origins-xenial.tgz
+upload_to_google_storage.py -b chromium-instrumented-libraries third_party/instrumented_libraries/binaries/msan-no-origins-xenial.tgz
 ```
 
 ## Testing and uploading a CL