Don't use a helper function to get the vertex attributes. The overhead of the function call ended up being a hot spot for draw calls since the attributes are iterated over many times in VertexDataManager. BUG=angleproject:959 Change-Id: I6c11d4a5a22c314c69b3403dfdeb2d950b1c7639 Reviewed-on: https://chromium-review.googlesource.com/262336 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Nicolas Capens <capn@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>