VertexArray: Don't syncState on Buffer map/unmap. Map/unmap calls are now treated like contents change events. Similar to BufferSubData calls. Bug: angleproject:6371 Change-Id: Ie0a4c521ffdedfa723d47eddd21c6f68dde044ac Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3187811 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com>