Move DropDownPreference to supportlib

Change-Id: Ife6799d1136302b805b5191f1a86276c538ca4bf
diff --git a/src/com/android/settings/DisplaySettings.java b/src/com/android/settings/DisplaySettings.java
index e9ab1f7..6d99a35 100644
--- a/src/com/android/settings/DisplaySettings.java
+++ b/src/com/android/settings/DisplaySettings.java
@@ -33,11 +33,13 @@
 import android.provider.SearchIndexableResource;
 import android.provider.Settings;
 import android.support.v14.preference.SwitchPreference;
+import android.support.v7.preference.DropDownPreference;
 import android.support.v7.preference.ListPreference;
 import android.support.v7.preference.Preference;
 import android.support.v7.preference.Preference.OnPreferenceChangeListener;
 import android.text.TextUtils;
 import android.util.Log;
+
 import com.android.internal.logging.MetricsLogger;
 import com.android.internal.view.RotationPolicy;
 import com.android.settings.dashboard.SummaryLoader;