docs(ngRepeat): document the sorting of object keys

See #6210

Author: petebacondarwin

src/ng/directive/ngRepeat.js

@@ -23,6 +23,29 @@
  * Creating aliases for these properties is possible with {@link ng.directive:ngInit `ngInit`}.
  * This may be useful when, for instance, nesting ngRepeats.
  *
+ * # Iterating over object properties
+ *
+ * It is possible to get `ngRepeat` to iterate over the properties of an object using the following
+ * syntax:
+ *
+ * ```js
+ * <div ng-repeat="(key, value) in myObj"> ... </div>
+ * ```
+ *
+ * You need to be aware that the JavaScript specification does not define what order
+ * it will return the keys for an object. In order to have a guaranteed deterministic order
+ * for the keys, Angular versions up to and including 1.3 **sort the keys alphabetically**.
+ *
+ * If this is not desired, the recommended workaround is to convert your object into an array
+ * that is sorted into the order that you prefer before providing it to `ngRepeat`.  You could
+ * do this with a filter such as [toArrayFilter](http://ngmodules.org/modules/angular-toArrayFilter)
+ * or implement a `$watch` on the object yourself.
+ *
+ * In version 1.4 we will remove the sorting, since it seems that browsers generally follow the
+ * strategy of providing keys in the order in which they were defined, although there are exceptions
+ * when keys are deleted and reinstated.
+ *
+ *
  * # Special repeat start and end points
  * To repeat a series of elements instead of just one parent element, ngRepeat (as well as other ng directives) supports extending
  * the range of the repeater by defining explicit start and end points by using **ng-repeat-start** and **ng-repeat-end** respectively.