Fix amnesia problem in MultiSelectListPreference.

Bug: 6478079

Pointer assignment instead of copy was resulting in mValues being cleared
on next launch, since mValues became the same pointer as mNewValues.

Change-Id: I91014948e4f48056474b3ab31aab6d35e0ad69ca

Author: Amith Yamasani

core/java/android/preference/MultiSelectListPreference.java

@@ -125,8 +125,9 @@ public CharSequence[] getEntryValues() {
      * @param values The values to set for the key.
      */
     public void setValues(Set<String> values) {
-        mValues = values;
-        
+        mValues.clear();
+        mValues.addAll(values);
+
         persistStringSet(values);
     }