Adding more icons to Launcher for tests

Virtual device comes with too few preinstalled icons, so All Apps can't
scroll, which make tests fail.

Change-Id: Ie0901f6d6fe645c530a66c417c0405ef31787543

tests/src/com/android/launcher3/testcomponent/MainActivity3.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.android.launcher3.testcomponent;
+
+import android.app.Activity;
+
+/**
+ * Base activity with utility methods to help automate testing.
+ */
+public class MainActivity3 extends Activity {
+}