Move implementation of hasMappedBuffer to State. Refactoring patch only. BUG=angle:571 Change-Id: Ib9f3145eaa457d94e488fd42eb4c4b9133768996 Reviewed-on: https://chromium-review.googlesource.com/210643 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org>