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..e0cd3cc12b58a46583592e61a22e8809bf294e95 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));
+  int64_t target_rate_kbps = int64_t{bitrate_bps} * bandwidth_usage_percent_ /

[kwiberg-webrtc, 2017/09/04 08:53:59]

Consider replacing the first "int64_t" with "auto". That way, you're guaranteed
to not get a narrowing conversion when you save the value to a temporary.

(Also consider making the temporary const. It's not all that necessary given
that it only lives one more line, but it's a good habit to get into.)

[oprypin_webrtc, 2017/09/04 09:09:21]

Done.

+                             (1000 * 100);
+  alr_budget_.set_target_rate_kbps(rtc::dchecked_cast<int>(target_rate_kbps));
 }
 
 rtc::Optional<int64_t> AlrDetector::GetApplicationLimitedRegionStartTime()