NS_ConvertUTF8toUTF16 and nsAString.EqualsASCII were failing as we didn't have ReadableUtils imported. So import that; it only builds in non-unified mode.
Change import.py so that it handles #else pre-processor directives in pref files; this was causing us to not get some prefs correctly.
Add test for every pref that we get the value that we expect.