Remove usage of ANGLE_FALLTHROUGH in EmulatePrecision.cpp BUG=chromium:810767 Change-Id: Ic0dafc9038b14093fdb799fe382ba8275195c0cc Reviewed-on: https://chromium-review.googlesource.com/914804 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>