Revert of Add support for single sample metrics.

components/metrics/single_sample_metrics_factory_impl.cc

-// 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.
-
-#include "components/metrics/single_sample_metrics_factory_impl.h"
-
-#include "base/threading/thread_checker.h"
-
-namespace metrics {
-
-namespace {
-
-class SingleSampleMetricImpl : public base::SingleSampleMetric {
- public:
-  SingleSampleMetricImpl(mojom::SingleSampleMetricPtr metric)
-      : metric_(std::move(metric)) {}
-
-  ~SingleSampleMetricImpl() override {
-    DCHECK(thread_checker_.CalledOnValidThread());
-  }
-
-  void SetSample(base::HistogramBase::Sample sample) override {
-    DCHECK(thread_checker_.CalledOnValidThread());
-    metric_->SetSample(sample);
-  }
-
- private:
-  base::ThreadChecker thread_checker_;
-  mojom::SingleSampleMetricPtr metric_;
-
-  DISALLOW_COPY_AND_ASSIGN(SingleSampleMetricImpl);
-};
-
-}  // namespace
-
-SingleSampleMetricsFactoryImpl::SingleSampleMetricsFactoryImpl(
-    CreateProviderCB create_provider_cb)
-    : create_provider_cb_(std::move(create_provider_cb)) {}
-
-SingleSampleMetricsFactoryImpl::~SingleSampleMetricsFactoryImpl() {}
-
-std::unique_ptr<base::SingleSampleMetric>
-SingleSampleMetricsFactoryImpl::CreateCustomCountsMetric(
-    const std::string& histogram_name,
-    base::HistogramBase::Sample min,
-    base::HistogramBase::Sample max,
-    uint32_t bucket_count) {
-  return CreateMetric(histogram_name, min, max, bucket_count,
-                      base::HistogramBase::kUmaTargetedHistogramFlag);
-}
-
-void SingleSampleMetricsFactoryImpl::DestroyProviderForTesting() {
-  if (auto* provider = provider_tls_.Get())
-    delete provider;
-  provider_tls_.Set(nullptr);
-}
-
-std::unique_ptr<base::SingleSampleMetric>
-SingleSampleMetricsFactoryImpl::CreateMetric(const std::string& histogram_name,
-                                             base::HistogramBase::Sample min,
-                                             base::HistogramBase::Sample max,
-                                             uint32_t bucket_count,
-                                             int32_t flags) {
-  mojom::SingleSampleMetricPtr metric;
-  GetProvider()->AcquireSingleSampleMetric(
-      histogram_name, min, max, bucket_count, flags,
-      mojo::MakeRequest<mojom::SingleSampleMetric>(&metric));
-  return base::MakeUnique<SingleSampleMetricImpl>(std::move(metric));
-}
-
-mojom::SingleSampleMetricsProvider*
-SingleSampleMetricsFactoryImpl::GetProvider() {
-  // Check the current TLS slot to see if we have created a provider already for
-  // this thread.
-  if (auto* provider = provider_tls_.Get())
-    return provider->get();
-
-  // If not, create a new one which will persist until process shutdown and put
-  // it in the TLS slot for the current thread.
-  mojom::SingleSampleMetricsProviderPtr* provider =
-      new mojom::SingleSampleMetricsProviderPtr();
-  provider_tls_.Set(provider);
-
-  // Start the provider connection and return it; it won't be fully connected
-  // until later, but mojo will buffer all calls prior to completion.
-  create_provider_cb_.Run(mojo::MakeRequest(provider));
-  return provider->get();
-}
-
-}  // namespace metrics