Update the FAQ: storing passwords on Linux

The previous description presumed parity between Mac and Linux, which
has not yet been implemented.

Change-Id: I1867d3cfe32cc61c277024921f504acf472eee35
Reviewed-on: https://chromium-review.googlesource.com/874450Reviewed-by: Vaclav Brozek <vabr@chromium.org>
Reviewed-by: Eric Lawrence <elawrence@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530470}

docs/security/faq.md

@@ -570,9 +570,10 @@ specific:
      credentials in "Login Data" in the Chrome users profile directory, but
      encrypted on disk with a key that is then stored in the user's Keychain.
      See [Issue 466638](https://crbug.com/466638) for further explanation.
-*    On Linux, credentials are stored in an encrypted database, and the password
-     to decrypt the contents of that database are stored in KWallet or Gnome
-     Keyring. (See [Issue 602624](https://crbug.com/602624).)
+*    On Linux, credentials are stored into Gnome-Keyring or KWallet, depending
+     on the environment. On environments which don't ship with Gnome-Keyring
+     or KWallet, the password is stored into "Login Data" in an unprotected
+     format.
 *    On iOS, passwords are currently stored directly in the iOS Keychain and
      referenced from the rest of the metadata stored in a separate DB. The plan
      there is to just store them in plain text in the DB, because iOS gives