function _getProvidersForLanguageId(languageId) {
        var providers = hintProviders[languageId] || hintProviders.all;

        // Exclude providers that are explicitly disabled in the preferences.
        // All code hint providers that do not have their constructor
        // names listed in the preferences are enabled by default.
        return providers.filter(function (provider) {
            var prefKey = "codehint." + provider.provider.constructor.name;
            return PreferencesManager.get(prefKey) !== false;
        });
    }
Return the array of hint providers for the given language id.
 This gets called (potentially) on every keypress. So, it should be fast.

@param {!string} languageId
@return {?Array.<{provider: Object, priority: number}>}