Apparently returning a small struct was slow enough to make a 2-3%
difference in benchmark scores. Very visible on the MSVC sampling
profiler.

Bug: angleproject:2747
Change-Id: I459a127f3f2a0fc3a08db15c37257a67f63f20ce
Reviewed-on: https://chromium-review.googlesource.com/1181465Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>