[Sync] Move //components/sync_driver to //components/sync/driver.

components/sync_driver/device_count_metrics_provider.h

-// Copyright 2016 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_SYNC_DRIVER_DEVICE_COUNT_METRICS_PROVIDER_H_
-#define COMPONENTS_SYNC_DRIVER_DEVICE_COUNT_METRICS_PROVIDER_H_
-
-#include <memory>
-#include <vector>
-
-#include "base/callback.h"
-#include "base/macros.h"
-#include "components/metrics/metrics_provider.h"
-
-namespace sync_driver {
-
-class DeviceInfoTracker;
-
-// A registerable metrics provider that will emit the number of active syncing
-// devices a user has upon UMA upload. When there are multiple active profiles
-// that are aware of syncable devices, the largest count is used. This approach
-// is useful for several reasons. We're significantly interested in "power"
-// users that have multiple devices and profiles, and if we skipped emitting any
-// metrics in multi profile cases, then we'd be unaware of this entire segment
-// of the population. If we emitted multiple metrics, we would have much more
-// noise and discerning which metrics actually belonged to non-syncing users
-// would be much trickier.
-class DeviceCountMetricsProvider : public metrics::MetricsProvider {
- public:
-  typedef base::Callback<void(
-      std::vector<const sync_driver::DeviceInfoTracker*>* trackers)>
-      ProvideTrackersCallback;
-
-  explicit DeviceCountMetricsProvider(
-      const ProvideTrackersCallback& provide_trackers);
-  ~DeviceCountMetricsProvider() override;
-
-  // MetricsProvider:
-  void ProvideGeneralMetrics(
-      metrics::ChromeUserMetricsExtension* uma_proto) override;
-
- private:
-  // Returns the max number of active devices across all accounts.
-  int MaxActiveDeviceCount() const;
-
-  const ProvideTrackersCallback provide_trackers_;
-
-  DISALLOW_COPY_AND_ASSIGN(DeviceCountMetricsProvider);
-};
-
-}  // namespace sync_driver
-
-#endif  // COMPONENTS_SYNC_DRIVER_DEVICE_COUNT_METRICS_PROVIDER_H_