tree 360f4f4b6280c9651b7fb72be1b439283dac5ddb
parent 667b9e7fcd69c19ee873641fd10c3367cfb75b9c
author Lingfeng Yang <lfy@google.com> 1570889940 -0700
committer Lingfeng Yang <lfy@google.com> 1571158389 -0700

gl2 encoder: async unmapbuffer

bug: 140112486

- No need to talk to the host if we glMapBufferRange with invalidation.
- No need to talk to the host if we glUnmapBuffer without wanting to
write.

Use the extension string to decide which to use, as it may or
may not be available on the host.

Change-Id: Ib50d24064d4c4d5517dc02b4d65f0f314f5d4ccf