docs: add info to SharedPreferences.Editor.putString
am: fb48521f41

Change-Id: I948c8091a70180e29a601d6cba40d7fb0cf2d76a
diff --git a/core/java/android/content/SharedPreferences.java b/core/java/android/content/SharedPreferences.java
index 7f9e176..4b09fed 100644
--- a/core/java/android/content/SharedPreferences.java
+++ b/core/java/android/content/SharedPreferences.java
@@ -72,7 +72,9 @@
          * {@link #commit} or {@link #apply} are called.
          * 
          * @param key The name of the preference to modify.
-         * @param value The new value for the preference.
+         * @param value The new value for the preference.  Passing {@code null}
+         *    for this argument is equivalent to calling {@link #remove(String)} with
+         *    this key.
          * 
          * @return Returns a reference to the same Editor object, so you can
          * chain put calls together.