WindowSurfaceGLX: swap before resizing the child window BUG=angleproject:892 Change-Id: I9b27777547624959fce6e045f9aac2652f139b9b Reviewed-on: https://chromium-review.googlesource.com/282058 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>