Re-enable UBsan on AGC.

webrtc/modules/audio_processing/agc/legacy/analog_agc.c

Index: webrtc/modules/audio_processing/agc/legacy/analog_agc.c
diff --git a/webrtc/modules/audio_processing/agc/legacy/analog_agc.c b/webrtc/modules/audio_processing/agc/legacy/analog_agc.c
index 36c67c282a02a1b9096f01aa8bda572624f8b67b..030077afe30aae60d2a611670cbaf0a0323e3015 100644
--- a/webrtc/modules/audio_processing/agc/legacy/analog_agc.c
+++ b/webrtc/modules/audio_processing/agc/legacy/analog_agc.c
@@ -476,16 +476,20 @@ void WebRtcAgc_ZeroCtrl(LegacyAgc* stt, int32_t* inMicLevel, int32_t* env) {
   int16_t i;
   int32_t tmp32 = 0;
   int32_t midVal;
+  const int kZeroThreshold = 500;
 
   /* Is the input signal zero? */
   for (i = 0; i < 10; i++) {
+    if (env[i] >= kZeroThreshold || tmp32 >= kZeroThreshold) {
+      break;

[peah-webrtc, 2016/06/03 08:27:12]

You still have not revised this according to your earlier comment about moving
to using a 64 bit variable.

[minyue-webrtc, 2016/06/03 08:32:32]

Ah! true. Thank you so much!

+    }
     tmp32 += env[i];
   }
 
   /* Each block is allowed to have a few non-zero
    * samples.
    */
-  if (tmp32 < 500) {
+  if (i == 10 && tmp32 < kZeroThreshold) {
     stt->msZero += 10;
   } else {
     stt->msZero = 0;