Fix BrowserMainLoop NSS ifdef for iOS.
Fix BrowserMainLoop NSS ifdef for iOS.

This file is still built on iOS. No bots broke but to avoid accidentally
changing behavior, use the more general USE_NSS_CERTS || !USE_OPENSSL
condition.

BUG=528468

Review URL: https://codereview.chromium.org/1328253002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#347776}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium