Add a Model to the download component.

components/download/internal/entry.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 COMPONENTS_DOWNLOAD_INTERNAL_DOWNLOAD_ENTRY_H_

[xingliu, 2017/05/09 06:11:41]

INTERNAL_ENTRY_H_.

[David Trainor- moved to gerrit, 2017/05/15 15:59:51]

Done.

+#define COMPONENTS_DOWNLOAD_INTERNAL_DOWNLOAD_ENTRY_H_
+
+#include "base/files/file_path.h"
+#include "base/optional.h"
+#include "base/time/time.h"

[xingliu, 2017/05/09 06:11:41]

nit: Maybe we can remove the above 3 headers.

[David Trainor- moved to gerrit, 2017/05/15 15:59:51]

Done.

+#include "components/download/public/client.h"
+#include "components/download/public/clients.h"
+#include "components/download/public/download_params.h"
+
+namespace download {
+
+// An entry in the Model that represents a scheduled download.
+struct Entry {
+ public:
+  enum class State {
+    // A newly added download.  The Entry is not guaranteed to be persisted in
+    // the model yet.
+    NEW = 0,
+
+    // The download has been persisted and is available to start, pending
+    // scheduler criteria.
+    AVAILABLE = 1,
+
+    // The download is active.  The DownloadDriver is aware of it and it is
+    // either being downloaded or suspended by the scheduler due to device
+    // characteristics or throttling.
+    ACTIVE = 2,
+
+    // The download has been paused by the owning Client.  The download will not
+    // be run until it is resumed by the Client.
+    PAUSED = 3,
+
+    // The download is 'complete' by some definition of that term (could have
+    // failed, could have succeeded, etc.).  It is ready to have UMA logs saved.
+    DUMP_STATS = 4,

[xingliu, 2017/05/09 06:11:41]

optional nit: not sure, but do we really like to make metric logging a separate
state?

[David Trainor- moved to gerrit, 2017/05/09 15:59:26]

Probably not.  I do want all logging for all possible exit points to go through
a single flow though (too easy to miss added points).

[Peter Beverloo, 2017/05/10 12:44:45]

If you want to validate state transitions, maybe just think of this as COMPLETE?

I guess all previous states can transition to this one (either through
completion, timeout or cancellation). You'd record UMA, which can be
synchronous, and then transition to WATCHDOG, requiring that for deleting the
data, even if it's immediate.

[David Trainor- moved to gerrit, 2017/05/15 15:59:51]

Yeah the plan was to pretty much immediately transition out of this state.  I'll
make it COMPLETE because that abstracts away exactly what the state is doing and
represents the state of the download at that point.  Thanks!

+
+    // The download is finished.  We are leaving this entry around to make sure
+    // the files on disk are cleaned up.
+    WATCHDOG = 5,
+  };
+
+  Entry();
+  Entry(const Entry& other);
+  ~Entry();
+
+  // The feature that is requesting this download.
+  DownloadClient client;
+
+  // A unique GUID that represents this download.  See | base::GenerateGUID()|.
+  std::string guid;
+
+  // The parameters that determine under what device conditions this download
+  // will occur.
+  SchedulingParams scheduling_params;
+
+  // The parameters that define the actual download request to make.
+  RequestParams request_params;
+
+  // The state of the download to help the scheduler and loggers make the right
+  // decisions about the download object.
+  State state;
+};
+
+}  // namespace download
+
+#endif  // COMPONENTS_DOWNLOAD_INTERNAL_MODEL_H_