shadows/framework/src/main/java/org/robolectric/shadows/ShadowSystem.java
@SuppressWarnings("unused")
  public static long nanoTime() {
    if (ShadowLooper.looperMode() == LooperMode.Mode.PAUSED) {
      return TimeUnit.MILLISECONDS.toNanos(SystemClock.uptimeMillis());
    } else {
      return ShadowLegacySystemClock.nanoTime();
    }
  }
@SuppressWarnings("unused")
  public static long nanoTime() {
    if (ShadowLooper.looperMode() == LooperMode.Mode.PAUSED) {
      return TimeUnit.MILLISECONDS.toNanos(SystemClock.uptimeMillis());
    } else {
      return ShadowLegacySystemClock.nanoTime();
    }
  }
Implements {@link System#nanoTime} through ShadowWrangler.

@return Current time with nanos.