Fix up perf test runner script.
Fix up perf test runner script.

The missing check was a bit buggy, and the paths were not updated
to the new 'gyp' folder instead of 'build'.

BUG=angleproject:1569

Change-Id: I10408252851e90b79e306c8aea175ebe6a931b61
Reviewed-on: https://chromium-review.googlesource.com/412320
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

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