This extension will be used by Chrome to advertise the visual it will
use for its windows. Having ANGLE use the same visual will bring
several benefits:
 - A blit will be avoided, and the content of the window might be
   rendered on the system framebuffer directly.
 - There will be less latency when resizing windows which will make it
   much less likely to see a black border when resizing.

BUG=522149

Change-Id: Icd484c9a948ed5b5b9116247bb50560bffa30667
Reviewed-on: https://chromium-review.googlesource.com/312323Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tryjob-Request: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>