Revert of Move vertex buffer setup out of drawPackedGlyph(). (https://codereview...

Revert of Move vertex buffer setup out of drawPackedGlyph(). (https://codereview.chromium.org/414573002/)

Reason for revert:
Breaking Ubuntu and Windows bots.

Original issue's description:
> Move vertex buffer setup out of drawPackedGlyph().
>
> This gets a very welcome ~10% speedup on my Mac.
>
> Committed: https://skia.googlesource.com/skia/+/1d38619389cc1100bd516b9acbf17b7bd42d33ce

R=bsalomon@google.com
TBR=bsalomon@google.com
NOTREECHECKS=true
NOTRY=true

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/419943002