This prevents overflow issues in the HLSL translator and some drivers. The
limit it hard-coded to 65536 to be larger than the Shader Model 5 register
limit (4096) to account for register allocation optimizations and future
hardware.

BUG=379799

Change-Id: I3cd0d8ad2084c3ca675821bfad1fab48f78c76c7
Reviewed-on: https://chromium-review.googlesource.com/204521Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Nicolas Capens <nicolascapens@chromium.org>