Create the BackgroundFetchBatchManager and initiate a download.

content/browser/background_fetch/background_fetch_batch_manager.h

+// Copyright 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_BACKGROUND_FETCH_BACKGROUND_FETCH_BATCH_MANAGER_H_
+#define CONTENT_BROWSER_BACKGROUND_FETCH_BACKGROUND_FETCH_BATCH_MANAGER_H_
+
+#include <unordered_map>
+
+#include "content/browser/background_fetch/fetch_request.h"

[Peter Beverloo, 2017/02/23 12:14:55]

...but you depend on them, so `git add` and re-upload please? :)

[harkness, 2017/02/23 17:08:41]

Done.

+#include "content/common/content_export.h"
+
+namespace content {
+
+class BrowserContext;
+class StoragePartition;
+
+class CONTENT_EXPORT BackgroundFetchBatchManager {

[Peter Beverloo, 2017/02/23 12:14:56]

nit: Please add a class-level comment. It'll be a good way to force us to keep
bits of documentation up-to-date as your ideas about the architecture change.

[harkness, 2017/02/23 17:08:41]

Done.

+ public:
+  BackgroundFetchBatchManager(BrowserContext* browser_context_,

[Peter Beverloo, 2017/02/23 12:14:55]

nit: s/browser_context_/browser_context/ (underscores are reserved for members.)

[harkness, 2017/02/23 17:08:41]

Done.

+                              StoragePartition* storage_partition);
+  ~BackgroundFetchBatchManager();
+
+  // Start processing on a batch of requests. Some of these may already be in
+  // progress or completed from a previous chromium instance.
+  void ProcessBatch(const std::string& batch_uid,
+                    const std::vector<FetchRequest>& requests);
+
+ private:
+  void ProcessRequest(const std::string& batch_uid,

[Peter Beverloo, 2017/02/23 12:14:55]

nit: `uid` is singular

[harkness, 2017/02/23 17:08:41]

Done.

+                      const FetchRequest& request);
+
+  // Pointer to the browser context. The BackgroundFetchBatchManager is owned by
+  // the BrowserContext via the StoragePartition.
+  BrowserContext* browser_context_;
+
+  // Pointer to the storage partition. This object is owned by the partition
+  // (through a sequence of other classes).
+  StoragePartition* storage_partition_;
+
+  // The fetch_map holds any requests which have been sent to the
+  // DownloadManager indexed by the batch_uid.
+  std::unordered_map<std::string, FetchRequest> fetch_map;

[Peter Beverloo, 2017/02/23 12:14:55]

nit: s/fetch_map/fetch_map_/ (members have underscore suffices.)

[Peter Beverloo, 2017/02/23 12:14:55]

This can end up making a lot of copies. Should FetchRequest be a
std::unique_ptr<>?

[harkness, 2017/02/23 17:08:41]

I'm using std::move now. Would you prefer unique_ptr?

[harkness, 2017/02/23 17:08:41]

Done.

[Peter Beverloo, 2017/02/24 02:05:15]

FetchRequest has no move constructor, so it will be *copied*, not *moved*. Even
if it had a move constructor, the number of operations it has to do in order to
move data will be higher than moving an std::unique_ptr<>.

+};

[Peter Beverloo, 2017/02/23 12:14:56]

DISALLOW_COPY_AND_ASSIGN()

[harkness, 2017/02/23 17:08:41]

Done.

+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_BACKGROUND_FETCH_BACKGROUND_FETCH_BATCH_MANAGER_H_