Fix warnings in PathRenderingTest.cpp. Certain warnings are suppressed in Chromium but not standalone ANGLE. We should enable those warnings for ANGLE specifically, in a follow-up CL. BUG=angleproject:1382 Change-Id: I12491a61b0f349c5937a1e5d9985c8da1d76e0dc Reviewed-on: https://chromium-review.googlesource.com/358107 Reviewed-by: Jamie Madill <jmadill@chromium.org>