remove SK_SUPPORT_LEGACY_DRAWVERTICES_VIRTUAL flag

BUG=skia:6366

Change-Id: If5e5bc2a65f2d8c66d7bef36cbb906c01225f80f
Reviewed-on: https://skia-review.googlesource.com/9940
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed