[CfT] Document default Chrome for Testing user data dir location

Chrome for Testing default user data dir location is different
from both Chrome and Chromium and is not documented.

This CL fixes this.

Bug: 369781731
Change-Id: Ied8a3dcb5c8ae82871c39d61c3343d8805bbca82
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5906384
Auto-Submit: Peter Kvitek <kvitekp@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1364155}
diff --git a/docs/user_data_dir.md b/docs/user_data_dir.md
index 29f3cfa..f4e2ad6 100644
--- a/docs/user_data_dir.md
+++ b/docs/user_data_dir.md
@@ -45,6 +45,7 @@
 * [Chrome] `%LOCALAPPDATA%\Google\Chrome\User Data`
 * [Chrome Beta] `%LOCALAPPDATA%\Google\Chrome Beta\User Data`
 * [Chrome Canary] `%LOCALAPPDATA%\Google\Chrome SxS\User Data`
+* [Chrome for Testing] `%LOCALAPPDATA%\Google\Chrome for Testing\User Data`
 * [Chromium] `%LOCALAPPDATA%\Chromium\User Data`
 
 (The canary channel suffix is determined using
@@ -57,6 +58,7 @@
 * [Chrome] `~/Library/Application Support/Google/Chrome`
 * [Chrome Beta] `~/Library/Application Support/Google/Chrome Beta`
 * [Chrome Canary] `~/Library/Application Support/Google/Chrome Canary`
+* [Chrome for Testing] `~/Library/Application Support/Google/Chrome for Testing`
 * [Chromium] `~/Library/Application Support/Chromium`
 
 (The canary channel suffix is determined using the `CrProductDirName` key in the
@@ -69,6 +71,7 @@
 * [Chrome Stable] `~/.config/google-chrome`
 * [Chrome Beta] `~/.config/google-chrome-beta`
 * [Chrome Dev] `~/.config/google-chrome-unstable`
+* [Chrome for Testing] `~/.config/google-chrome-for-testing`
 * [Chromium] `~/.config/chromium`
 
 (The beta and dev channel suffixes are determined from `$CHROME_VERSION_EXTRA`,