x11: Always require XI2.2 for X11.

x11: Always require XI2.2 for X11.

This removes the use_xi2_mt gyp variable, and USE_XI2_MT define from the
code. XI2.2 is now available on all supported linux platforms.

BUG=291141
R=brettw@chromium.org, derat@chromium.org, erg@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/4ae87941c77264d9271afdf939381962c4f45bd2

[sadrul, 2014-11-11 21:30:55]

sadrul@chromium.org changed reviewers:
+ derat@chromium.org, eglaysher@chromium.org

[Daniel Erat, 2014-11-11 22:12:25]

lgtm

[sadrul, 2014-11-11 23:47:34]

sadrul@chromium.org changed reviewers:
+ erg@chromium.org
- eglaysher@chromium.org

[sadrul, 2014-11-11 23:47:34]

-eglaysher@ +erg@

[sadrul, 2014-11-11 23:50:29]

sadrul@chromium.org changed reviewers:
+ brettw@chromium.org

[sadrul, 2014-11-11 23:50:30]

brettw@chromium.org: Please review changes in //build/config

[brettw, 2014-11-12 05:31:26]

BUILD.gn LGTM

[Elliot Glaysher, 2014-11-12 18:28:55]

lgtm

[commit-bot: I haz the power, 2014-11-12 23:23:06]

Patchset 3 (id:??) landed as
https://crrev.com/4ae87941c77264d9271afdf939381962c4f45bd2
Cr-Commit-Position: refs/heads/master@{#303918}

[sadrul, 2014-11-12 23:23:11]

Committed patchset #3 (id:40001) manually as
4ae87941c77264d9271afdf939381962c4f45bd2 (presubmit successful).

[dmazzoni, 2015-03-18 20:37:10]

dmazzoni@chromium.org changed reviewers:
+ dmazzoni@chromium.org

[dmazzoni, 2015-03-18 20:37:11]

Is it possible this is the cause of http://crbug.com/456222? Lots of Linux users
are reporting a major regression for almost anything involving the mouse when
using Virtualbox.

This change was in the bisect.