IWYU for thread_pool.h

Simply adding base/task/thread_pool.h to any file
using "base::ThreadPool::" (and not having the include
in its matching header).

Prereq for https://chromium-review.googlesource.com/c/chromium/src/+/2773408

Bug: 1026641
Change-Id: I46c19c8acf6f6d6d7b83c8a40568d5194a591251
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2775891
Commit-Queue: Gabriel Charette <[email protected]>
Commit-Queue: François Doray <[email protected]>
Auto-Submit: Gabriel Charette <[email protected]>
Reviewed-by: François Doray <[email protected]>
Owners-Override: François Doray <[email protected]>
Cr-Commit-Position: refs/heads/master@{#864771}
diff --git a/components/reporting/encryption/decryption.cc b/components/reporting/encryption/decryption.cc
index 9efa787..82b257e 100644
--- a/components/reporting/encryption/decryption.cc
+++ b/components/reporting/encryption/decryption.cc
@@ -15,6 +15,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/task/post_task.h"
+#include "base/task/thread_pool.h"
 #include "base/task_runner.h"
 #include "components/reporting/encryption/encryption.h"
 #include "components/reporting/util/status.h"