Connect BackgroundFetch to the OfflineItemCollection

content/public/browser/background_fetch_client.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_PUBLIC_BROWSER_BACKGROUND_FETCH_CLIENT_H_
+#define CONTENT_PUBLIC_BROWSER_BACKGROUND_FETCH_CLIENT_H_
+
+#include <string>
+
+#include "content/common/content_export.h"
+
+namespace content {
+
+// The BackgroundFetchClient provides a communication path for BackgroundFetch
+// to use functionality provided by embedders to display offline content and
+// notifications about ongoing BackgroundFetch operations. It also provides a
+// mechanism for BackgroundFetch to provide a Delegate to allow embedders to
+// control ongoing BackgroundFetch operations.

[Peter Beverloo, 2017/03/31 01:32:24]

We use "Background Fetch" w/ space elsewhere.

I wonder if we should generalize this description, since we don't really know
what (or how) other embedders will use it. Maybe they'd Pause or Resume based on
network quality assessments?

What about:

// The Background Fetch client enables the embedder to be given information
// about the active Background Fetches, for example to provide a user interface,
// and for the embedder to control the state of such fetches.

[harkness, 2017/03/31 10:11:45]

Done.

+class CONTENT_EXPORT BackgroundFetchClient {
+ public:
+  // Class for access to the BackgroundFetch system. Manages in progress fetches
+  // and supports pause, resume, cancel, and UI update.
+  class CONTENT_EXPORT Delegate {
+   public:
+    // Cancel all fetches associated with the |registration_id|.
+    virtual void CancelDownload(const std::string& registration_id) = 0;
+
+    // Pause all fetches associated with the |registration_id|.
+    virtual void PauseDownload(const std::string& registration_id) = 0;
+
+    // Resume any fetches associated with the |registration_id|.
+    virtual void ResumeDownload(const std::string& registration_id) = 0;
+
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  // The Delegate provided is owned by the content layer. If a
+  // delegate has ever been set through SetDelegate, the content layer
+  // guarantees to call SetDelegate with |nullptr| before destroying the
+  // existing delegate.

[Peter Beverloo, 2017/03/31 01:32:24]

The content layer is rather large and hard to reason about. What about:

// The client will maintain a weak reference to |delegate|. The provider must
// reset the delegate back to a `nullptr` when it's being destructed.

[harkness, 2017/03/31 10:11:44]

Done.

+  virtual void SetDelegate(Delegate* delegate) = 0;
+
+  virtual ~BackgroundFetchClient() {}

[Peter Beverloo, 2017/03/31 01:32:24]

Can this be protected?

[harkness, 2017/03/31 10:11:45]

Done.

+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_BACKGROUND_FETCH_CLIENT_H_