docs: Clarified how multi-window applies to activities in task stack

Per bug, devs were confused about behavior of activities in a
task stack. Added a note to clarify that MW settings in the root
activity apply to all activities in stack.

See first comment for doc stage location.

bug: 27870811
Change-Id: Ifb22815e06f4040f155ec52ff5bacc81da1efbfb
diff --git a/docs/html/preview/features/multi-window.jd b/docs/html/preview/features/multi-window.jd
index a12ab94..9527905 100644
--- a/docs/html/preview/features/multi-window.jd
+++ b/docs/html/preview/features/multi-window.jd
@@ -162,7 +162,9 @@
   whether your app's activities support multi-window display. You can set
   attributes in your manifest to control both size and layout.
   A root activity's attribute settings apply to all activities
-  within its task stack.
+  within its task stack. For example, if the root activity has
+  <code>android:resizeableActivity</code> set to true, then all activities
+  in the task stack are resizeable.
 </p>
 
 <p class="note">