Revert changes made in http://ag/2388716 as we have few open questions
about the performance loss because of this CL.

Change-Id: I4c499b176dbd80a31f2088ece27346077fbbcdec
Bug: 62466540
diff --git a/src/com/android/launcher3/util/MultiHashMap.java b/src/com/android/launcher3/util/MultiHashMap.java
index 2b29085..b7275c1 100644
--- a/src/com/android/launcher3/util/MultiHashMap.java
+++ b/src/com/android/launcher3/util/MultiHashMap.java
@@ -16,13 +16,13 @@
 
 package com.android.launcher3.util;
 
-import android.support.v4.util.ArrayMap;
 import java.util.ArrayList;
+import java.util.HashMap;
 
 /**
  * A utility map from keys to an ArrayList of values.
  */
-public class MultiHashMap<K, V> extends ArrayMap<K, ArrayList<V>> {
+public class MultiHashMap<K, V> extends HashMap<K, ArrayList<V>> {
 
     public MultiHashMap() { }