docs(toJson): documented the Safari RangeError known issue

Closes #14221
Closes #13415

Author: petebacondarwin

src/Angular.js

@@ -1233,6 +1233,27 @@ function toJsonReplacer(key, value) {
  * @param {boolean|number} [pretty=2] If set to true, the JSON output will contain newlines and whitespace.
  *    If set to an integer, the JSON output will contain that many spaces per indentation.
  * @returns {string|undefined} JSON-ified string representing `obj`.
+ * @knownIssue
+ *
+ * The Safari browser throws a `RangeError` instead of returning `null` when it tries to stringify a `Date`
+ * object with an invalid date value. The only reliable way to prevent this is to monkeypatch the
+ * `Date.prototype.toJSON` method as follows:
+ *
+ * ```
+ * var _DatetoJSON = Date.prototype.toJSON;
+ * Date.prototype.toJSON = function() {
+ *   try {
+ *     return _DatetoJSON.call(this);
+ *   } catch(e) {
+ *     if (e instanceof RangeError) {
+ *       return null;
+ *     }
+ *     throw e;
+ *   }
+ * };
+ * ```
+ *
+ * See https://github.com/angular/angular.js/pull/14221 for more information.
  */
 function toJson(obj, pretty) {
   if (isUndefined(obj)) return undefined;