[GLX] Don't request exposure events for child windows
[GLX] Don't request exposure events for child windows

After [1], Chrome and ANGLE use separate X11 connections, so in order
for Chrome to receive exposure events, it must select for them its own
connection, which is done in [2].

The events selected by ANGLE's connection are never dispatched, so
they queue up indefinitely and leak until the connection is closed
(when happens when Chrome closes).  This change removes the request
to receive exposure events.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/2492177
[2] https://chromium-review.googlesource.com/c/chromium/src/+/2602441

Change-Id: Ie47c3700855aeeecc8efa1b379df60c344b1b70a
Bug: chromium:1158170
R=jonahr
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2602705
Reviewed-by: Jonah Ryan-Davis <682bdb9e7d8ba359ef169b8db374e7a99d394a46@google.com>
Commit-Queue: Jonah Ryan-Davis <682bdb9e7d8ba359ef169b8db374e7a99d394a46@google.com>

ppy/angle,ppy/angle,ppy/angle,ppy/angle