Pass current value type instead of the object. This allows us to simplify the logic in VertexDataManager enough that we can start to cache attribute information. BUG=angleproject:959 Change-Id: I7b53a137d73f40f86e3acb9caebb66f9cacf8b6f Reviewed-on: https://chromium-review.googlesource.com/277283 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>