docs: Updates to multi-window and related docs.

Clarified behavior when activity is resized or put in fullscreen
mode, per b/28580007 . Also (per email from o-o) removed misleading
statement about when onStop() might or might not be called.

Both changes can go live now (multiwindow update applies to DP1 & 2,
and onStop() clarification applies to all versions of API), so I'll
submit as soon as this is approved.

See first comment for doc stage location.

bug: 28580007
Change-Id: Ib008f24e5796ec7810b67c91e512e679680d4afd

core/java/android/app/Activity.java

@@ -1593,10 +1593,6 @@ public class Activity extends ContextThemeWrapper
      * receive either {@link #onRestart}, {@link #onDestroy}, or nothing,
      * depending on later user activity.
      *
-     * <p>Note that this method may never be called, in low memory situations
-     * where the system does not have enough memory to keep your activity's
-     * process running after its {@link #onPause} method is called.
-     *
      * <p><em>Derived classes must call through to the super class's
      * implementation of this method.  If they do not, an exception will be
      * thrown.</em></p>

docs/html/preview/features/multi-window.jd

@@ -138,7 +138,9 @@ page.keywords="multi-window", "android N", "split screen", "free-form"
   When the user puts an app into multi-window mode, the system notifies the
   activity of a configuration change, as specified in <a href=
   "{@docRoot}guide/topics/resources/runtime-changes.html">Handling Runtime
-  Changes</a>. Essentially, this change has the same activity-lifecycle
+  Changes</a>. This also happens when the user resizes the app, or puts the app
+  back into full-screen mode.
+  Essentially, this change has the same activity-lifecycle
   implications as when the system notifies the app that the device has switched
   from portrait to landscape mode, except that the device dimensions are
   changed instead of just being swapped. As discussed in <a href=