[BIC] Enable the creation of mock apps

We can populate mock background installed apps by setting the
value of "debug.transparency.bg-install-apps".
The string value is the list of names of the mock apps.

Bug: 266888785
Test: Run `adb shell setprop
      debug.transparency.bg-install-apps
      <some existing apps>`
      to set the list of mock apps.
      Run `adb shell cmd transparency get mba_info`
      to check existence of the apps.
Change-Id: I07a6106937a8217c16c31cbacf967d3c2102a2b1

services/core/java/com/android/server/pm/BackgroundInstallControlService.java

@@ -27,12 +27,15 @@ import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManagerInternal;
 import android.content.pm.ParceledListSlice;
+import android.os.Build;
 import android.os.Environment;
 import android.os.Handler;
 import android.os.Looper;
 import android.os.Message;
 import android.os.SystemClock;
+import android.os.SystemProperties;
 import android.os.UserHandle;
+import android.text.TextUtils;
 import android.util.ArraySet;
 import android.util.AtomicFile;
 import android.util.Slog;
@@ -51,6 +54,7 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Set;
@@ -122,7 +126,18 @@ public class BackgroundInstallControlService extends SystemService {
         @Override
         public ParceledListSlice<PackageInfo> getBackgroundInstalledPackages(
                 @PackageManager.PackageInfoFlagsBits long flags, int userId) {
-            return mService.getBackgroundInstalledPackages(flags, userId);
+            if (!Build.IS_DEBUGGABLE) {
+                return mService.getBackgroundInstalledPackages(flags, userId);
+            }
+            // The debug.transparency.bg-install-apps (only works for debuggable builds)
+            // is used to set mock list of background installed apps for testing.
+            // The list of apps' names is delimited by ",".
+            String propertyString = SystemProperties.get("debug.transparency.bg-install-apps");
+            if (TextUtils.isEmpty(propertyString)) {
+                return mService.getBackgroundInstalledPackages(flags, userId);
+            } else {
+                return mService.getMockBackgroundInstalledPackages(propertyString);
+            }
         }
     }
 
@@ -145,6 +160,27 @@ public class BackgroundInstallControlService extends SystemService {
         return new ParceledListSlice<>(packages);
     }
 
+    /**
+     * Mock a list of background installed packages based on the property string.
+     */
+    @NonNull
+    ParceledListSlice<PackageInfo> getMockBackgroundInstalledPackages(
+            @NonNull String propertyString) {
+        String[] mockPackageNames = propertyString.split(",");
+        List<PackageInfo> mockPackages = new ArrayList<>();
+        for (String name : mockPackageNames) {
+            try {
+                PackageInfo packageInfo = mPackageManager.getPackageInfo(name,
+                        PackageManager.PackageInfoFlags.of(PackageManager.MATCH_ALL));
+                mockPackages.add(packageInfo);
+            } catch (PackageManager.NameNotFoundException e) {
+                Slog.w(TAG, "Package's PackageInfo not found " + name);
+                continue;
+            }
+        }
+        return new ParceledListSlice<>(mockPackages);
+    }
+
     private static class EventHandler extends Handler {
         private final BackgroundInstallControlService mService;