Set the return value in FenceSyncNULL::clientWait.
Set the return value in FenceSyncNULL::clientWait.

BUG=angleproject:1468

Change-Id: I3cf0d0a9486778b1d4384e00359034e08e425191
Reviewed-on: https://chromium-review.googlesource.com/414284
Reviewed-by: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>

MSOpenTech/angle,ecoal95/angle,ecoal95/angle,ppy/angle,MSOpenTech/angle,ecoal95/angle,ppy/angle,MSOpenTech/angle,ppy/angle,MSOpenTech/angle,ppy/angle,ecoal95/angle,ecoal95/angle