Create component to expose network usage stats to consumers.

components/data_usage/core/data_use.h

+// Copyright 2015 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_DATA_USAGE_CORE_DATA_USE_H_
+#define COMPONENTS_DATA_USAGE_CORE_DATA_USE_H_
+
+#include <stdint.h>
+
+#include "base/time/time.h"
+#include "net/base/network_change_notifier.h"
+#include "url/gurl.h"
+
+namespace data_usage {
+
+struct DataUse {
+  DataUse(const GURL& url,
+          const base::Time& request_time,
+          const GURL& first_party_for_cookies,
+          int tab_id,

[bengr, 2015/10/06 19:30:28]

Perhaps we should use a const std::string& tab_label instead, because we might
need to augment the tab annotation beyond an ID.

[tbansal1, 2015/10/06 20:13:15]

There is a tab_id field in Chromium
(which is int32) which is unique across all tabs and is monotonically
increasing. 
We should keep that in the struct. Would tab annotation be maintained
by data_usage component? I was expecting it to be separate.

[sclittle, 2015/10/07 01:07:55]

Changed to int32_t according to tbansal's comment.

If we do need to handle tab annotations, then that annotation could either be a
separate field in this struct or just maintained by the observer that cares
about it.

+          net::NetworkChangeNotifier::ConnectionType connection_type,
+          int64_t tx_bytes,
+          int64_t rx_bytes);
+
+  GURL url;
+  // The time that the request that is associated with these bytes was started.
+  base::Time request_time;
+  GURL first_party_for_cookies;
+  int tab_id;
+  net::NetworkChangeNotifier::ConnectionType connection_type;
+  // TODO(sclittle): Add more network info here, e.g. for Android, SIM operator
+  // and whether the device is roaming.
+
+  int64_t tx_bytes;
+  int64_t rx_bytes;
+};
+
+}  // namespace data_usage
+
+#endif  // COMPONENTS_DATA_USAGE_CORE_DATA_USE_H_