In the doc, Google says NSS would need to be added to the base Android image.. so it's not going to be updated any faster than openSSL.
When powering WebView, Chromium on Android uses the Android system-provided OpenSSL library - something not available to applications building with the Android NDK (like Chrome for Android or other Chromium-based Android applications). This helps reduce memory usage by having a single shared library in memory. To accomplish this with NSS, NSS would have to be part of the Android base image - which would still increase memory usage, as most other Android (native) services would still use OpenSSL.
