Documentation for "not_allowed" value in "incognito" manifest field.

chrome/common/extensions/docs/templates/articles/manifest/incognito.html

Index: chrome/common/extensions/docs/templates/articles/manifest/incognito.html
diff --git a/chrome/common/extensions/docs/templates/articles/manifest/incognito.html b/chrome/common/extensions/docs/templates/articles/manifest/incognito.html
index 967a208b127715e6b970670a56a1decaa255c563..c55de0b8bb5a4cdb234b7d7ec2f78aef4714fe23 100644
--- a/chrome/common/extensions/docs/templates/articles/manifest/incognito.html
+++ b/chrome/common/extensions/docs/templates/articles/manifest/incognito.html
@@ -3,7 +3,9 @@
 <p>
 Use the <code>"incognito"</code> manifest key with either
 <code>"spanning"</code> or <code>"split"</code> to specify how this
-{{platform}} will behave if allowed to run in incognito mode.
+{{platform}} will behave if allowed to run in incognito mode. Using <code>
+"not_allowed"</code> to prevent this {{platform}} from being enabled in
+incognito mode.
 </p>
 
 <p>
@@ -35,6 +37,11 @@ cookie store. Each process sees events and messages only from its own context
 processes are unable to communicate with each other.
 </p>
 
+<h2 id="not_allowed">Not allowed</h2>
+<p>
+The {{platform}} cannot be enabled in incognito mode. Available from Chrome 47.
+</p>
+
 <h2 id="how-to-choose">How to choose</h2>
 <p>
 As a rule of thumb, if your extension or app needs to load a tab in an