Replace std::vector in NQE by an array

Replace std::vector in Network Quality Estimator (NQE) by an array.
This is an attempt to avoid the crash that happens only on
Windows when rtt_ms_observations_ vector is referenced.

Change-Id: I8a3e0e45be6881bfb02442a62c7403aaa5b8078f
Bug: 899808
TBR: ryansturm@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/1343345Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Doug Arnett <dougarnett@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609530}

net/nqe/network_quality_estimator.cc

@@ -17,6 +17,7 @@
 #include "base/metrics/histogram_functions.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
+#include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/stringprintf.h"
@@ -230,6 +231,22 @@ NetworkQualityEstimator::NetworkQualityEstimator(
           tick_clock_,
           params_->weight_multiplier_per_second(),
           params_->weight_multiplier_per_signal_strength_level()),
+      rtt_ms_observations_{
+          ObservationBuffer(
+              params_.get(),
+              tick_clock_,
+              params_->weight_multiplier_per_second(),
+              params_->weight_multiplier_per_signal_strength_level()),
+          ObservationBuffer(
+              params_.get(),
+              tick_clock_,
+              params_->weight_multiplier_per_second(),
+              params_->weight_multiplier_per_signal_strength_level()),
+          ObservationBuffer(
+              params_.get(),
+              tick_clock_,
+              params_->weight_multiplier_per_second(),
+              params_->weight_multiplier_per_signal_strength_level())},
       effective_connection_type_at_last_main_frame_(
           EFFECTIVE_CONNECTION_TYPE_UNKNOWN),
       effective_connection_type_recomputation_interval_(
@@ -246,12 +263,8 @@ NetworkQualityEstimator::NetworkQualityEstimator(
           net::NetLogSourceType::NETWORK_QUALITY_ESTIMATOR)),
       event_creator_(net_log_),
       weak_ptr_factory_(this) {
-  rtt_ms_observations_.reserve(nqe::internal::OBSERVATION_CATEGORY_COUNT);
-  for (int i = 0; i < nqe::internal::OBSERVATION_CATEGORY_COUNT; ++i) {
-    rtt_ms_observations_.push_back(ObservationBuffer(
-        params_.get(), tick_clock_, params_->weight_multiplier_per_second(),
-        params_->weight_multiplier_per_signal_strength_level()));
-  }
+  DCHECK_EQ(nqe::internal::OBSERVATION_CATEGORY_COUNT,
+            base::size(rtt_ms_observations_));
 
   network_quality_store_.reset(new nqe::internal::NetworkQualityStore());
   NetworkChangeNotifier::AddConnectionTypeObserver(this);
@@ -695,6 +708,8 @@ bool NetworkQualityEstimator::RequestProvidesRTTObservation(
 void NetworkQualityEstimator::OnConnectionTypeChanged(
     NetworkChangeNotifier::ConnectionType type) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  DCHECK_EQ(nqe::internal::OBSERVATION_CATEGORY_COUNT,
+            base::size(rtt_ms_observations_));
 
   // Write the estimates of the previous network to the cache.
   network_quality_store_->Add(
@@ -1232,6 +1247,8 @@ base::TimeDelta NetworkQualityEstimator::GetRTTEstimateInternal(
     int percentile,
     size_t* observations_count) const {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  DCHECK_EQ(nqe::internal::OBSERVATION_CATEGORY_COUNT,
+            base::size(rtt_ms_observations_));
 
   // RTT observations are sorted by duration from shortest to longest, thus
   // a higher percentile RTT will have a longer RTT than a lower percentile.
@@ -1480,6 +1497,8 @@ void NetworkQualityEstimator::OnNewThroughputObservationAvailable(
 
 bool NetworkQualityEstimator::ShouldComputeEffectiveConnectionType() const {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  DCHECK_EQ(nqe::internal::OBSERVATION_CATEGORY_COUNT,
+            base::size(rtt_ms_observations_));
 
   const base::TimeTicks now = tick_clock_->NowTicks();
   // Recompute effective connection type only if

net/nqe/network_quality_estimator.h

@@ -567,11 +567,11 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
 
   // Buffer that holds RTT observations with different observation categories.
   // The entries in |rtt_ms_observations_| are in the same order as the
-  // entries in the nqe::internal:ObservationCategory enum.  Size of
-  // |rtt_ms_observations_| is nqe::internal::OBSERVATION_CATEGORY_COUNT.
+  // entries in the nqe::internal:ObservationCategory enum.
   // Each observation buffer in |rtt_ms_observations_| stores RTT observations
   // in milliseconds. Within a buffer, the observations are sorted by timestamp.
-  std::vector<ObservationBuffer> rtt_ms_observations_;
+  ObservationBuffer
+      rtt_ms_observations_[nqe::internal::OBSERVATION_CATEGORY_COUNT];
 
   // Time when the transaction for the last main frame request was started.
   base::TimeTicks last_main_frame_request_;