NetEq: Fix a bug in expand_rate and speech_expand_rate calculation

webrtc/modules/audio_coding/neteq/statistics_calculator.cc

Index: webrtc/modules/audio_coding/neteq/statistics_calculator.cc
diff --git a/webrtc/modules/audio_coding/neteq/statistics_calculator.cc b/webrtc/modules/audio_coding/neteq/statistics_calculator.cc
index b47ca127dbe7a2107b4315a7bd4eece1ef0d19fa..51807069e7a67ea79fe65b8b97e4e440c9b23fd9 100644
--- a/webrtc/modules/audio_coding/neteq/statistics_calculator.cc
+++ b/webrtc/modules/audio_coding/neteq/statistics_calculator.cc
@@ -15,6 +15,7 @@
 #include <algorithm>
 
 #include "webrtc/base/checks.h"
+#include "webrtc/base/safe_compare.h"
 #include "webrtc/base/safe_conversions.h"
 #include "webrtc/modules/audio_coding/neteq/decision_logic.h"
 #include "webrtc/modules/audio_coding/neteq/delay_manager.h"
@@ -22,6 +23,17 @@
 
 namespace webrtc {
 
+namespace {
+size_t AddIntToSizeTWithLowerCap(int a, size_t b) {
+  if (rtc::safe_cmp::Gt(-int64_t{a}, b)) {
+    // Simply doing a + b would give a negative result, with a negative wrap.
+    // Cap it to zero instead.
+    return 0;
+  }
+  return rtc::dchecked_cast<size_t>(a) + b;
+}
+}
+
 // Allocating the static const so that it can be passed by reference to
 // RTC_DCHECK.
 const size_t StatisticsCalculator::kLenWaitingTimes;
@@ -148,6 +160,16 @@ void StatisticsCalculator::ExpandedNoiseSamples(size_t num_samples) {
   expanded_noise_samples_ += num_samples;
 }
 
+void StatisticsCalculator::ExpandedVoiceSamplesCorrection(int num_samples) {
+  expanded_speech_samples_ =
+      AddIntToSizeTWithLowerCap(num_samples, expanded_speech_samples_);
+}
+
+void StatisticsCalculator::ExpandedNoiseSamplesCorrection(int num_samples) {
+  expanded_noise_samples_ =
+      AddIntToSizeTWithLowerCap(num_samples, expanded_noise_samples_);
+}
+
 void StatisticsCalculator::PreemptiveExpandedSamples(size_t num_samples) {
   preemptive_samples_ += num_samples;
 }