Address review comments.

Author: vkryachko

firebase-annotations/src/main/java/com/google/firebase/annotations/concurrent/Background.java

@@ -21,6 +21,9 @@
 /**
  * An executor/coroutine dispatcher for long running tasks including disk IO, heavy CPU
  * computations.
+ *
+ * <p>For operations that can block for long periods of time, like network requests, use the {@link
+ * Blocking} executor.
  */
 @Qualifier
 @Target({ElementType.PARAMETER, ElementType.METHOD, ElementType.FIELD})

firebase-annotations/src/main/java/com/google/firebase/annotations/concurrent/Lightweight.java

@@ -19,7 +19,7 @@
 import javax.inject.Qualifier;
 
 /**
- * An executor/coroutine dispatcher for lightweight tasks that never block(on IO or other tasks).
+ * An executor/coroutine dispatcher for lightweight tasks that never block (on IO or other tasks).
  */
 @Qualifier
 @Target({ElementType.PARAMETER, ElementType.METHOD, ElementType.FIELD})

firebase-common/src/test/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright 2019 Google LLC -->
+<!-- Copyright 2022 Google LLC -->
 <!-- -->
 <!-- Licensed under the Apache License, Version 2.0 (the "License"); -->
 <!-- you may not use this file except in compliance with the License. -->

tools/lint/src/main/kotlin/CheckRegistry.kt

@@ -29,7 +29,7 @@ class CheckRegistry : IssueRegistry() {
                 NonAndroidxNullabilityDetector.NON_ANDROIDX_NULLABILITY,
                 DeferredApiDetector.INVALID_DEFERRED_API_USE,
                 ProviderAssignmentDetector.INVALID_PROVIDER_ASSIGNMENT
-                // TODO(vkryachko): enable the check after migration.
+                // TODO(vkryachko): enable the check after suppressing current violations.
                 // ThreadPoolDetector.THREAD_POOL_CREATION
         )