Obey the bufSize and write to the length parameter in glGetSynciv. BUG=angleproject:1985 TEST=conformance2/state/gl-object-get-calls Change-Id: Ic83c408b60d394ff5719beaedc5d4721b7811a47 Reviewed-on: https://chromium-review.googlesource.com/474551 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>