Fix use of references with va_start BUG=angle:736 va_start behavior is undefined if the second parameter is a function, array, or reference type. clang produces a warning for this, while MSVC does not. Change-Id: I0bc2805e312e3542aac816f10a257e2f1cfad128 Reviewed-on: https://chromium-review.googlesource.com/216010 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Nico Weber <thakis@chromium.org> Tested-by: Nico Weber <thakis@chromium.org>