Revert of Add support for single sample metrics.

components/metrics/single_sample_metrics_factory_impl.h

Index: components/metrics/single_sample_metrics_factory_impl.h
diff --git a/components/metrics/single_sample_metrics_factory_impl.h b/components/metrics/single_sample_metrics_factory_impl.h
deleted file mode 100644
index 297324f97b7a32b1d53623975797d71393a27b26..0000000000000000000000000000000000000000
--- a/components/metrics/single_sample_metrics_factory_impl.h
+++ /dev/null
@@ -1,71 +0,0 @@
-// 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_VALUE_HISTOGRAM_FACTORY_IMPL_H_
-#define COMPONENTS_METRICS_SINGLE_VALUE_HISTOGRAM_FACTORY_IMPL_H_
-
-#include <string>
-
-#include "base/metrics/single_sample_metrics.h"
-#include "base/threading/thread_local.h"
-#include "components/metrics/public/interfaces/single_sample_metrics.mojom.h"
-#include "components/metrics/single_sample_metrics.h"
-
-namespace metrics {
-
-// SingleSampleMetricsFactory implementation for creating SingleSampleMetric
-// instances that communicate over mojo to instances in another process.
-//
-// Persistance outside of the current process allows these metrics to record a
-// sample even in the event of sudden process termination. As an example, this
-// is useful for garbage collected objects which may never get a chance to run
-// their destructors in the event of a fast shutdown event (process kill).
-class SingleSampleMetricsFactoryImpl : public base::SingleSampleMetricsFactory {
- public:
-  // Constructs a factory capable of vending single sample metrics from any
-  // thread. |create_provider_cb| will be called from arbitrary threads to
-  // create providers as necessary; the callback must handle thread safety.
-  //
-  // We use a callback here to avoid taking additional DEPS on content and a
-  // service_manager::Connector() for simplicitly and to avoid the need for
-  // using the service test harness just for instantiating this class.
-  explicit SingleSampleMetricsFactoryImpl(CreateProviderCB create_provider_cb);
-  ~SingleSampleMetricsFactoryImpl() override;
-
-  // base::SingleSampleMetricsFactory:
-  std::unique_ptr<base::SingleSampleMetric> CreateCustomCountsMetric(
-      const std::string& histogram_name,
-      base::HistogramBase::Sample min,
-      base::HistogramBase::Sample max,
-      uint32_t bucket_count) override;
-
-  // Providers live forever in production, but tests should be kind and clean up
-  // after themselves to avoid tests trampling on one another. Destroys the
-  // provider in the TLS slot for the calling thread.
-  void DestroyProviderForTesting();
-
- private:
-  // Creates a single sample metric.
-  std::unique_ptr<base::SingleSampleMetric> CreateMetric(
-      const std::string& histogram_name,
-      base::HistogramBase::Sample min,
-      base::HistogramBase::Sample max,
-      uint32_t bucket_count,
-      int32_t flags);
-
-  // Gets the SingleSampleMetricsProvider for the current thread. If none
-  // exists, then a new instance is created and set in the TLS slot.
-  mojom::SingleSampleMetricsProvider* GetProvider();
-
-  CreateProviderCB create_provider_cb_;
-
-  // Per thread storage slot for the mojo provider.
-  base::ThreadLocalPointer<mojom::SingleSampleMetricsProviderPtr> provider_tls_;
-
-  DISALLOW_COPY_AND_ASSIGN(SingleSampleMetricsFactoryImpl);
-};
-
-}  // namespace metrics
-
-#endif  // COMPONENTS_METRICS_SINGLE_VALUE_HISTOGRAM_FACTORY_IMPL_H_