docs(guide/Expressions): added special case for one-time binding of object literals under Value stabilization algorithm

One time binding of object literals are treated differently than simple expressions. Added a link to Ben Nadel's article describing how object literals's keys are checked for undefined.

Closes #11982

Author: pholly

docs/content/guide/expression.ngdoc

@@ -28,13 +28,13 @@ Angular expressions are like JavaScript expressions with the following differenc
 
   * **No Control Flow Statements:** You cannot use the following in an Angular expression:
     conditionals, loops, or exceptions.
-	
+
   * **No Function Declarations:** You cannot declare functions in an Angular expression,
     even inside `ng-init` directive.
-	
-  * **No RegExp Creation With Literal Notation:** You cannot create regular expressions 
+
+  * **No RegExp Creation With Literal Notation:** You cannot create regular expressions
     in an Angular expression.
-	
+
   * **No Comma And Void Operators:** You cannot use `,` or `void` in an Angular expression.
 
   * **Filters:** You can use {@link guide/filter filters} within expressions to format data before
@@ -175,7 +175,7 @@ expression, delegate to a JavaScript method instead.
 ## No function declarations or RegExp creation with literal notation
 
 You can't declare functions or create regular expressions from within AngularJS expressions. This is
-to avoid complex model transformation logic inside templates. Such logic is better placed in a 
+to avoid complex model transformation logic inside templates. Such logic is better placed in a
 controller or in a dedicated filter where it can be tested properly.
 
 ## `$event`
@@ -303,10 +303,14 @@ then the expression is not fulfilled and will remain watched.
      keep dirty-checking the watch in the future digest loops by following the same
      algorithm starting from step 1
 
+#### Special case for object literals
+
+Unlike simple values, object-literals are watched until every key is defined.
+See http://www.bennadel.com/blog/2760-one-time-data-bindings-for-object-literal-expressions-in-angularjs-1-3.htm
 
 ### How to benefit from one-time binding
 
-If the expression will not change once set, it is a candidate for one-time binding. 
+If the expression will not change once set, it is a candidate for one-time binding.
 Here are three example cases.
 
 When interpolating text or attributes: