Revert of Implement THROTTLED priority semantics.

net/base/percentile_estimator.cc

Index: net/base/percentile_estimator.cc
diff --git a/net/base/percentile_estimator.cc b/net/base/percentile_estimator.cc
deleted file mode 100644
index 7b3d9cf0c168c1ba97adbde05515541341e3cdf6..0000000000000000000000000000000000000000
--- a/net/base/percentile_estimator.cc
+++ /dev/null
@@ -1,100 +0,0 @@
-// Copyright 2016 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 "percentile_estimator.h"
-
-#include "base/bind.h"
-#include "base/callback.h"
-#include "base/rand_util.h"
-
-namespace {
-
-// Random number wrapper to allow substitutions for testing.
-int GenerateRand0To99() {
-  return base::RandInt(0, 99);
-}
-
-}  // namespace
-
-namespace net {
-
-// The algorithm used for percentile estimation is "Algorithm 3" from
-// https://arxiv.org/pdf/1407.1121v1.pdf.  There are several parts to the
-// algorithm:
-// * The estimate is conditionally moved towards the sample by a step amount.
-//   This means that if the samples are clustered around a value the estimates
-//   will converge to that sample.
-// * The percentile requested (e.g. 90%l) is handled by the conditional move.
-//   If the estimate is accurate, there is a chance equal to the percentile
-//   value that a sample will be lower than it, and a chance equal to
-//   1-percentile that it will be higher.  So the code balances those
-//   probabilities by increasing the estimate in the percentile fraction
-//   of the cases where the sample is over the estimate, and decreases the
-//   estimate in (1-percentile) fraction of the cases where the sample is under
-//   the estimate.
-//   E.g. in the case of the 90%l estimation, the estimate would
-//   move up in 90% of the cases in which the sample was above the
-//   estimate (which would be 10% of the total samples, presuming the
-//   estimate was accurate), and it would move down in 10% of the cases
-//   in which the sample was below the estimate.
-// * Every time the estimate moves in the same direction, the step
-//   amount is increased by one, and every time the estimate reverses
-//   direction, the step amount is decreased (to 1, if greater than 1,
-//   by one, if zero or negative).  The effective step amount is
-//   Max(step, 1).
-// * If the estimate
-//   would be moved beyond the sample causing its move, it is moved to
-//   be equal to the same (and the step amount set to the distance to
-//   the sample).  See the paper for further details.
-
-PercentileEstimator::PercentileEstimator(int percentile, int initial_estimate)
-    : percentile_(percentile),
-      sign_positive_(true),
-      current_estimate_(initial_estimate),
-      current_step_(1),
-      generator_callback_(base::Bind(&GenerateRand0To99)) {}
-
-PercentileEstimator::~PercentileEstimator() {}
-
-void PercentileEstimator::AddSample(int sample) {
-  int rand100 = generator_callback_.Run();
-  if (sample > current_estimate_ && rand100 > 1 - percentile_) {
-    current_step_ += sign_positive_ ? 1 : -1;
-    current_estimate_ += (current_step_ > 0) ? current_step_ : 1;
-
-    // Clamp movement to distance to sample.
-    if (current_estimate_ > sample) {
-      current_step_ -= current_estimate_ - sample;
-      current_estimate_ = sample;
-    }
-
-    // If we've reversed direction, reset the step down.
-    if (!sign_positive_ && current_step_ > 1)
-      current_step_ = 1;
-
-    sign_positive_ = true;
-  } else if (sample < current_estimate_ && rand100 > percentile_) {
-    current_step_ += !sign_positive_ ? 1 : -1;
-    current_estimate_ -= (current_step_ > 0) ? current_step_ : 1;
-
-    // Clamp movement to distance to sample.
-    if (current_estimate_ < sample) {
-      current_step_ -= sample - current_estimate_;
-      current_estimate_ = sample;
-    }
-
-    // If we've reversed direction, reset the step down.
-    if (sign_positive_ && current_step_ > 1)
-      current_step_ = 1;
-
-    sign_positive_ = false;
-  }
-}
-
-void PercentileEstimator::SetRandomNumberGeneratorForTesting(
-    RandomNumberCallback generator_callback) {
-  generator_callback_ = generator_callback;
-}
-
-}  // namespace net