Cap number of items we attempt to collapse

Cap number of items we attempt to collapse at 20. Algorithm used is n^2
and introduces noticeable delays with eg 70 phone numbers for a single contact.

Bug:8888517
Change-Id: Ifaa470a3dd91b783db23d5c694af4529cfbf1293

src/com/android/contacts/common/Collapser.java

@@ -32,6 +32,12 @@ public final class Collapser {
      */
     private Collapser() {}
 
+    /*
+     * The Collapser uses an n^2 algorithm so we don't want it to run on
+     * lists beyond a certain size. This specifies the maximum size to collapse.
+     */
+    private static final int MAX_LISTSIZE_TO_COLLAPSE = 20;
+
     /*
      * Interface implemented by data types that can be collapsed into groups of similar data. This
      * can be used for example to collapse similar contact data items into a single item.
@@ -51,6 +57,10 @@ public interface Collapsible<T> {
     public static <T extends Collapsible<T>> void collapseList(List<T> list) {
 
         int listSize = list.size();
+        // The algorithm below is n^2 so don't run on long lists
+        if (listSize > MAX_LISTSIZE_TO_COLLAPSE) {
+            return;
+        }
 
         for (int i = 0; i < listSize; i++) {
             T iItem = list.get(i);