Make UBSan warnings fatal and fix the existing ones

webrtc/modules/pacing/alr_detector.cc

Index: webrtc/modules/pacing/alr_detector.cc
diff --git a/webrtc/modules/pacing/alr_detector.cc b/webrtc/modules/pacing/alr_detector.cc
index 7d62b212511c56be3c0a779445fdeb1fa434bd8c..62b7f1a0a85c0d7e27e0024f79bfdd6161def01a 100644
--- a/webrtc/modules/pacing/alr_detector.cc
+++ b/webrtc/modules/pacing/alr_detector.cc
@@ -67,8 +67,9 @@ void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t delta_time_ms) {
 
 void AlrDetector::SetEstimatedBitrate(int bitrate_bps) {
   RTC_DCHECK(bitrate_bps);
-  alr_budget_.set_target_rate_kbps(bitrate_bps * bandwidth_usage_percent_ /
-                                   (1000 * 100));
+  double target_rate_kbps = static_cast<double>(bitrate_bps) / 1000 *
+                            bandwidth_usage_percent_ / 100;
+  alr_budget_.set_target_rate_kbps(rtc::dchecked_cast<int>(target_rate_kbps));

[kwiberg-webrtc, 2017/09/03 02:39:47]

Why not use int64_t here instead of double? It'll be faster, more deterministic,
and give results bit-identical to those of the current implementation.

[oprypin_webrtc, 2017/09/04 08:36:07]

Done.

 }
 
 rtc::Optional<int64_t> AlrDetector::GetApplicationLimitedRegionStartTime()