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

@return Current time with millis.