Revert of Add support for single sample metrics.

components/metrics/single_sample_metrics.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_METRICS_SINGLE_SAMPLE_METRICS_H_
-#define COMPONENTS_METRICS_SINGLE_SAMPLE_METRICS_H_
-
-#include "base/callback.h"
-#include "components/metrics/public/interfaces/single_sample_metrics.mojom.h"
-#include "services/service_manager/public/cpp/bind_source_info.h"
-
-namespace metrics {
-
-using CreateProviderCB =
-    base::RepeatingCallback<void(mojom::SingleSampleMetricsProviderRequest)>;
-
-// Initializes and sets the base::SingleSampleMetricsFactory for the current
-// process. |create_provider_cb| is used to create provider instances per each
-// thread that the factory is used on; this is necessary since the underlying
-// providers must only be used on the same thread as construction.
-//
-// We use a callback here to avoid taking additional DEPS on content and a
-// service_manager::Connector() for simplicity and to avoid the need for
-// using the service test harness in metrics unittests.
-//
-// Typically this is called in the process where termination may occur without
-// warning; e.g. perhaps a renderer process.
-extern void InitializeSingleSampleMetricsFactory(
-    CreateProviderCB create_provider_cb);
-
-// Creates a mojom::SingleSampleMetricsProvider capable of vending single sample
-// metrics attached to a mojo pipe.
-//
-// Typically this is given to a service_manager::BinderRegistry in the process
-// that has a deterministic shutdown path and which serves as a stable endpoint
-// for the factory created by the above initialize method in another process.
-extern void CreateSingleSampleMetricsProvider(
-    const service_manager::BindSourceInfo& source_info,
-    mojom::SingleSampleMetricsProviderRequest request);
-
-}  // namespace metrics
-
-#endif  // COMPONENTS_METRICS_SINGLE_SAMPLE_METRICS_H_