Fix test failure in CI

Author: lfkellogg

firebase-appdistribution/src/main/java/com/google/firebase/appdistribution/impl/ApkUpdater.java

@@ -110,8 +110,7 @@ private void installApk(File file, boolean showDownloadNotificationManager) {
             activity -> apkInstaller.installApk(file.getPath(), activity))
         .addOnSuccessListener(lightweightExecutor, unused -> cachedUpdateTask.setResult())
         .addOnFailureListener(
-            // TODO(lkellogg): check if this can switch to lightweight (uses NotificationManager)
-            blockingExecutor,
+            lightweightExecutor,
             e -> {
               postUpdateProgress(
                   file.length(),

firebase-appdistribution/src/main/java/com/google/firebase/appdistribution/impl/TaskCache.java

@@ -16,8 +16,6 @@
 
 import com.google.android.gms.tasks.Task;
 
-// TODO: replace this with TaskCompletionSourceCache and UpdateTaskCache, then rename
-// TaskCompletionSourceCache to TaskCache
 /**
  * A cache for Tasks, for use in cases where we only ever want one active task at a time for a
  * particular operation.

firebase-appdistribution/src/test/java/com/google/firebase/appdistribution/impl/ApkUpdaterTest.java

@@ -183,6 +183,18 @@ public void updateApk_whenSuccessfullyUpdated_notificationsSetCorrectly()
     doReturn(new ByteArrayInputStream(TEST_FILE.getBytes()))
         .when(mockHttpsUrlConnection)
         .getInputStream();
+    // Sleep thread to simulate actually making the request, which gives us time to add
+    // a listener to the returned UpdateTask in time to get all the progress updates
+    when(mockHttpsUrlConnectionFactory.openConnection(TEST_URL))
+        .thenAnswer(
+            invocation -> {
+              try {
+                Thread.sleep(100);
+              } catch (InterruptedException e) {
+                throw new AssertionError("Interrupted while sleeping in mock");
+              }
+              return mockHttpsUrlConnection;
+            });
     doNothing().when(apkUpdater).validateJarFile(any(), anyLong(), anyBoolean(), anyLong());
     when(mockApkInstaller.installApk(any(), any())).thenReturn(Tasks.forResult(null));