[reland] Use TaskScheduler instead of blocking pool in file_downloader.cc.

chrome/browser/net/file_downloader.cc

Index: chrome/browser/net/file_downloader.cc
diff --git a/chrome/browser/net/file_downloader.cc b/chrome/browser/net/file_downloader.cc
index ffbb4f96680d0740295fe45f3f16c8f93ff18e63..f8f3f792d8fa597dfe1e517d8197dca738985274 100644
--- a/chrome/browser/net/file_downloader.cc
+++ b/chrome/browser/net/file_downloader.cc
@@ -8,7 +8,7 @@
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
-#include "base/threading/sequenced_worker_pool.h"
+#include "base/task_scheduler/post_task.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/load_flags.h"
 #include "net/http/http_status_code.h"
@@ -43,9 +43,12 @@ FileDownloader::FileDownloader(
     fetcher_->Start();
   } else {
     base::PostTaskAndReplyWithResult(
-        BrowserThread::GetBlockingPool()
-            ->GetTaskRunnerWithShutdownBehavior(
-                base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN)
+        base::CreateTaskRunnerWithTraits(
+            base::TaskTraits()
+                .MayBlock()
+                .WithPriority(base::TaskPriority::BACKGROUND)
+                .WithShutdownBehavior(
+                    base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN))
             .get(),
         FROM_HERE, base::Bind(&base::PathExists, local_path_),
         base::Bind(&FileDownloader::OnFileExistsCheckDone,
@@ -82,9 +85,12 @@ void FileDownloader::OnURLFetchComplete(const net::URLFetcher* source) {
   }
 
   base::PostTaskAndReplyWithResult(
-      BrowserThread::GetBlockingPool()
-          ->GetTaskRunnerWithShutdownBehavior(
-              base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN)
+      base::CreateTaskRunnerWithTraits(
+          base::TaskTraits()
+              .MayBlock()
+              .WithPriority(base::TaskPriority::BACKGROUND)
+              .WithShutdownBehavior(
+                  base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN))
           .get(),
       FROM_HERE, base::Bind(&base::Move, response_path, local_path_),
       base::Bind(&FileDownloader::OnFileMoveDone,