NetworkQualityEstimator: Enable prefs writing by default

net/nqe/network_quality_estimator.cc

 // Copyright 2015 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 "net/nqe/network_quality_estimator.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <utility>
@@ skipping 122 matching lines @@
 const int32_t kBitsPerMetric = 7;
 
 static_assert(32 >= kBitsPerMetric * 4,
               "Four metrics would not fit in a 32-bit int");
 
 // Trims the |metric| by removing the last kTrimBits, and then rounding down
 // the |metric| such that the |metric| fits in kBitsPerMetric.
 int32_t FitInKBitsPerMetricBits(int32_t metric) {
   // Remove the last kTrimBits. This will allow the metric to fit within
   // kBitsPerMetric while losing only the least significant bits.
+  DCHECK_LE(0, metric);
   metric = metric >> kTrimBits;
 
   // kLargestValuePossible is the largest value that can be recorded using
   // kBitsPerMetric.
   static const int32_t kLargestValuePossible = (1 << kBitsPerMetric) - 1;
   if (metric > kLargestValuePossible) {
     // Fit |metric| in kBitsPerMetric by clamping it down.
     metric = kLargestValuePossible;
   }
-  DCHECK_EQ(0, metric >> kBitsPerMetric);
+  DCHECK_EQ(0, metric >> kBitsPerMetric) << metric;
   return metric;
 }
 
 void RecordRTTAccuracy(const char* prefix,
                        int32_t metric,
                        base::TimeDelta measuring_duration,
                        base::TimeDelta observed_rtt) {
   const std::string histogram_name =
       base::StringPrintf("%s.EstimatedObservedDiff.%s.%d.%s", prefix,
                          metric >= 0 ? "Positive" : "Negative",
@@ skipping 436 matching lines @@
   // Record UMA only for successful requests that have completed.
   if (net_error != OK)
     return;
   if (!request.response_info().headers.get() ||
       request.response_info().headers->response_code() != HTTP_OK) {
     return;
   }
   if (load_timing_info.receive_headers_end < last_main_frame_request_)
     return;
 
-  const base::TimeTicks now = tick_clock_->NowTicks();
+  // Use the system clock instead of |tick_clock_| to compare the current
+  // timestamp with the |load_timing_info| timestamp since the latter is set by
+  // the system clock, and may be different from |tick_clock_| in tests.
+  const base::TimeTicks now = base::TimeTicks::Now();
   // Record UMA only for requests that started recently.
   if (now - last_main_frame_request_ > base::TimeDelta::FromSeconds(15))
     return;
 
   DCHECK_GE(now, load_timing_info.send_start);
 
   int32_t rtt = 0;
 
   if (UseTransportRTT()) {
     rtt = estimated_quality_at_last_main_frame_.transport_rtt() !=
@@ skipping 1059 matching lines @@
         NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP_CACHED_ESTIMATE);
     downstream_throughput_kbps_observations_.AddObservation(
         throughput_observation);
     NotifyObserversOfThroughput(throughput_observation);
   }
 
   ComputeEffectiveConnectionType();
 }
 
 }  // namespace net