Remove usage of SequencedWorkerPool::GetNamedSequenceToken from content::CreateFileSystemContext.

content/browser/fileapi/browser_file_system_helper.cc

Index: content/browser/fileapi/browser_file_system_helper.cc
diff --git a/content/browser/fileapi/browser_file_system_helper.cc b/content/browser/fileapi/browser_file_system_helper.cc
index f8da5a6ad26f684a8592e39cfae1dc7ddd741780..9fef5be45db124092bf39ee8a39e0d86e72e8a85 100644
--- a/content/browser/fileapi/browser_file_system_helper.cc
+++ b/content/browser/fileapi/browser_file_system_helper.cc
@@ -13,7 +13,7 @@
 #include "base/files/file_path.h"
 #include "base/sequenced_task_runner.h"
 #include "base/strings/utf_string_conversions.h"
-#include "base/threading/sequenced_worker_pool.h"
+#include "base/task_scheduler/post_task.h"
 #include "content/browser/child_process_security_policy_impl.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
@@ -63,12 +63,6 @@ scoped_refptr<storage::FileSystemContext> CreateFileSystemContext(
     const base::FilePath& profile_path,
     bool is_incognito,
     storage::QuotaManagerProxy* quota_manager_proxy) {
-  base::SequencedWorkerPool* pool = BrowserThread::GetBlockingPool();
-  scoped_refptr<base::SequencedTaskRunner> file_task_runner =
-      pool->GetSequencedTaskRunnerWithShutdownBehavior(
-          pool->GetNamedSequenceToken("FileAPI"),

[fdoray, 2017/05/17 14:38:49]

Mutual exclusion is guaranteed between tasks posted to SequencedTaskRunners
sharing the same named sequence token. With my CL, no named sequence token is
used, which means that the file SequencedTaskRunners of different
storage::FileSystemContext instances may run their tasks concurrently. Is this
ok?

-          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
-
   // Setting up additional filesystem backends.
   std::vector<std::unique_ptr<storage::FileSystemBackend>> additional_backends;
   GetContentClient()->browser()->GetAdditionalFileSystemBackends(
@@ -85,7 +79,10 @@ scoped_refptr<storage::FileSystemContext> CreateFileSystemContext(
   scoped_refptr<storage::FileSystemContext> file_system_context =
       new storage::FileSystemContext(
           BrowserThread::GetTaskRunnerForThread(BrowserThread::IO).get(),
-          file_task_runner.get(),
+          base::CreateSequencedTaskRunnerWithTraits(
+              {base::MayBlock(), base::TaskPriority::BACKGROUND,
+               base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN})
+              .get(),
           BrowserContext::GetMountPoints(browser_context),
           browser_context->GetSpecialStoragePolicy(), quota_manager_proxy,
           std::move(additional_backends), url_request_auto_mount_handlers,