Revert "Add UMA Histogram Manager to Cronet."

components/metrics/histogram_encoder.h

-// Copyright 2014 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.
-
-// This file defines an utility function that records any changes in a given
-// histogram for transmission.
-
-#ifndef COMPONENTS_METRICS_HISTOGRAM_ENCODER_H_
-#define COMPONENTS_METRICS_HISTOGRAM_ENCODER_H_
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "components/metrics/proto/chrome_user_metrics_extension.pb.h"
-
-namespace base {
-class HistogramSamples;
-}
-
-namespace metrics {
-
-// Record any changes (histogram deltas of counts from |snapshot|) into
-// |uma_proto| for the given histogram (|histogram_name|).
-void EncodeHistogramDelta(const std::string& histogram_name,
-                          const base::HistogramSamples& snapshot,
-                          ChromeUserMetricsExtension* uma_proto);
-
-}  // namespace metrics
-
-#endif  // COMPONENTS_METRICS_HISTOGRAM_ENCODER_H_