Use TaskScheduler instead of blocking pool in io_thread.cc.

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 3afae54e364f3fe05dd06c614a07d12b65af789b..4a8e711cf599c4a61df6a0c09776a8a1b129b1ed 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -26,7 +26,7 @@
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
-#include "base/threading/sequenced_worker_pool.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/threading/thread.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
@@ -1080,9 +1080,12 @@ net::URLRequestContext* IOThread::ConstructProxyScriptFetcherContext(
   job_factory->SetProtocolHandler(
       url::kFileScheme,
       base::MakeUnique<net::FileProtocolHandler>(
-          content::BrowserThread::GetBlockingPool()
-              ->GetTaskRunnerWithShutdownBehavior(
-                  base::SequencedWorkerPool::SKIP_ON_SHUTDOWN)));
+          base::CreateTaskRunnerWithTraits(
+              base::TaskTraits()
+                  .MayBlock()
+                  .WithPriority(base::TaskPriority::BACKGROUND)

[cbentzel, 2017/04/25 05:52:26]

This will be used for loading file:// URLs which may have some user visible
impact. Should this be USER_VISIBLE instead?

[fdoray, 2017/04/26 19:40:42]

Done.

+                  .WithShutdownBehavior(
+                      base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN))));
 #if !BUILDFLAG(DISABLE_FTP_SUPPORT)
   job_factory->SetProtocolHandler(
       url::kFtpScheme,