WindowSurfaceCGL: make resizing work correctly. Previously the code didn't resize the depth buffer. Also adds a magic setNeedsDisplay call when resizing a CALayer. BUG=angleproject:1233 Change-Id: Id1906312f58d474e95a1b5ebfc15eff4344cd126 Reviewed-on: https://chromium-review.googlesource.com/318450 Tryjob-Request: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>