Downloads: replace BrowserThread::FILE with task scheduler.

content/browser/download/download_task_runner.h

Index: content/browser/download/download_task_runner.h
diff --git a/content/browser/download/download_task_runner.h b/content/browser/download/download_task_runner.h
new file mode 100644
index 0000000000000000000000000000000000000000..dd4e192a8ce34c6a6aa360947f0f63f0e4c35f77
--- /dev/null
+++ b/content/browser/download/download_task_runner.h
@@ -0,0 +1,18 @@
+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_TASK_RUNNER_H_
+#define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_TASK_RUNNER_H_
+
+#include "base/sequenced_task_runner.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// Returns the task runner used to save files and do other blocking operations.
+CONTENT_EXPORT scoped_refptr<base::SequencedTaskRunner> GetDownloadTaskRunner();

[gab, 2017/06/22 16:03:59]

None of the callers require a refptr (some are even forced to .get()), I'm going
to update the LazyTaskRunner API to return a raw ptr by default instead to avoid
unnecessary ref churn. In the meantime if you're so inclined this could return a
SequencedTaskRunner* and the impl can .Get().get() with a TODO assigned to me +
issue 730170.

[gab, 2017/06/22 16:10:18]

Nvm, looks like you do need the refptr in one place for CreateByteStream().

[Sigurður Ásgeirsson, 2017/06/22 18:47:28]

Acknowledged.

[Sigurður Ásgeirsson, 2017/06/22 18:47:28]

Acknowledged.

+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_TASK_RUNNER_H_