function assertHighEntropyAPIsInUACHFallbackMode() {
  assertNull(
      'UserAgentData present - high-entropy APIs will be unexpectedly running in UACH mode',
      util.getUserAgentData());
}
Asserts that any usages of High-entropy API surfaces won't actually be able
to use UACH data (and should likely fall back to pre-UACH codepaths).