Make the doc for PreferenceScreen aware of PreferenceFragment.

This class has existed from before, so the doc does not mention
PreferenceFragment but only PreferenceActivity, while actually
the class can be used via PreferenceFragment.

Change-Id: Ie3756f7ff260cff829eff31a6ba99260c681bc2d
diff --git a/core/java/android/preference/PreferenceScreen.java b/core/java/android/preference/PreferenceScreen.java
index f34f4a3..c7f8ab2 100644
--- a/core/java/android/preference/PreferenceScreen.java
+++ b/core/java/android/preference/PreferenceScreen.java
@@ -91,7 +91,8 @@
 
     /**
      * Returns an adapter that can be attached to a {@link PreferenceActivity}
-     * to show the preferences contained in this {@link PreferenceScreen}.
+     * or {@link PreferenceFragment} to show the preferences contained in this
+     * {@link PreferenceScreen}.
      * <p>
      * This {@link PreferenceScreen} will NOT appear in the returned adapter, instead
      * it appears in the hierarchy above this {@link PreferenceScreen}.