The StreamDraw usage flag was changed to a static type in
http://crrev.com/50eb1e6f77b3b0ad89d2cd00efc0d1d673365296 but it appears to
have regressed performance in several Chrome benchmarks because
Skia uses it as a usage flag for buffers that change data frequently.

BUG=angleproject:3366
BUG=953788
BUG=954028

Change-Id: Ib6805d94714bcd1679f3c9c49f1b70574f0b658a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1582786Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Geoff Lang <geofflang@chromium.org>