Add error-handling when getting Xcb window size We can't trust the reply from Xcb if an error has been flagged. This was causing a crash in SwANGLE. Bug: chromium:1080984 Change-Id: Icaf58197869b563e4193efcf4e70646d519210cf Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2209255 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>