These perf tests use the D3D NULL renderers to measure pure CPU
time, with no GPU limitations. Also fix our D3D9 SwapChain code
to skip creating a SwapChain for NULLREF D3D9 devices, and the
vertex decl code to reinitialize the formats when finding a
mismatch with the previous value.

BUG=angleproject:955

Change-Id: I449e63177b48afd1559c36244de0bc252814e813
Reviewed-on: https://chromium-review.googlesource.com/262208Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>