Revert of Add support for single sample metrics.

components/metrics/public/interfaces/single_sample_metrics.mojom

-// 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.
-
-module metrics.mojom;
-
-// See components/metrics/single_sample_metrics_factory_impl.h for details.
-interface SingleSampleMetricsProvider {
-  // Returns a SingleSampleMetric.
-  //
-  // A single sample metric only reports its sample once at destruction time.
-  // The sample may be changed prior to destruction using the SetSample() method
-  // as many times as desired.
-  //
-  // See base/metrics/histograms.h for parameter definitions. |request| is the
-  // returned histogram.
-  AcquireSingleSampleMetric(string histogram_name, int32 min, int32 max,
-                            uint32 bucket_count, int32 flags,
-                            SingleSampleMetric& request);
-};
-
-interface SingleSampleMetric {
-  SetSample(int32 sample);
-};