Fix TaplTestsNexus#testSearchForApp

This cl is 1/2 part change

We are currently getting StaleObjectException when running this test.
We want to implment a synchoronized event beetween test and launcher,
so we know that search result adapter is done updating and page will
get no more updates of search results.

Test: Presubmit
Bug: 232008758
Flag: not needed
Change-Id: I40cf9b83d231a2487220aabc8f8e8c3ca71f255c

src/com/android/launcher3/FastScrollRecyclerView.java

@@ -16,6 +16,8 @@
 
 package com.android.launcher3;
 
+import static com.android.launcher3.testing.shared.TestProtocol.SCROLL_FINISHED_MESSAGE;
+
 import android.content.Context;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
@@ -170,7 +172,8 @@ public abstract class FastScrollRecyclerView extends RecyclerView  {
         super.onScrollStateChanged(state);
 
         if (state == SCROLL_STATE_IDLE) {
-            AccessibilityManagerCompat.sendScrollFinishedEventToTest(getContext());
+            AccessibilityManagerCompat.sendTestProtocolEventToTest(getContext(),
+                    SCROLL_FINISHED_MESSAGE);
         }
     }