Extract counting of installed apps into helper class

This CL extracts the code that counts the number of installed apps
for a set of users from ManageApplications to a helper class,
InstalledAppCounter. The new helper is designed to be unit-testable
(PackageManager dependencies are injected via a new PackageManagerWrapper
abstraction) and customizable (the set of users for which to count is
specified by subclasses).

The CL adds a unit test for the InstalledAppCounter as well.

Test: make RunSettingsRoboTests
Bug: 32692748
Change-Id: Ie7fbd40d9dd998b27f1f9de227b6a187b5c9d315

tests/robotests/src/com/android/settings/testutils/ApplicationTestUtils.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2016 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.settings.testutils;
+
+import android.content.pm.ApplicationInfo;
+import android.os.UserHandle;
+
+/**
+ * Helper for mocking installed applications.
+ */
+public class ApplicationTestUtils {
+    /**
+     * Create and populate an {@link android.content.pm.ApplicationInfo} object that describes an
+     * installed app.
+     *
+     * @param userId The user id that this app is installed for. Typical values are 0 for the
+     *         system user and 10, 11, 12... for secondary users.
+     * @param packageName The app's package name.
+     * @param flags Flags describing the app. See {@link android.content.pm.ApplicationInfo#flags}
+     *         for possible values.
+     *
+     * @see android.content.pm.ApplicationInfo
+     */
+    public static ApplicationInfo buildInfo(int userId, String packageName, int flags) {
+        final ApplicationInfo info = new ApplicationInfo();
+        info.uid = UserHandle.getUid(userId, 1);
+        info.packageName = packageName;
+        info.flags = flags;
+        return info;
+    }
+}