This attempts to reduce the amount of redundant validation done
between indexed draw calls. It keeps the cached info in the
VertexArray11 class.

It also includes a fix to a missing direct buffer invalidation in
CopyBufferSubData which was turning up with the new caching.

Reduces overhead in the D3D11 indexed rendering perf test such that it
leads to an increased score of about 20%.

BUG=angleproject:2229

Change-Id: I63121bea19a9c8198e1925ed6a1460838e8f8955
Reviewed-on: https://chromium-review.googlesource.com/765262
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>