Fix for left-shift of potentially negative values in NetEq.

Left shifting negative integers is undefined behavior, and should be prevented. This CL fixes one such instance in the NetEq Expand function.

BUG=chromium:677106

Review-Url: https://codereview.webrtc.org/2616363003
Cr-Commit-Position: refs/heads/master@{#15966}
diff --git a/webrtc/modules/audio_coding/neteq/expand.cc b/webrtc/modules/audio_coding/neteq/expand.cc
index da870d7..2154bfd 100644
--- a/webrtc/modules/audio_coding/neteq/expand.cc
+++ b/webrtc/modules/audio_coding/neteq/expand.cc
@@ -441,7 +441,7 @@
   for (size_t i = 0; i < kNumCorrelationCandidates; ++i) {
     int32_t ratio;
     if (best_distortion[i] > 0) {
-      ratio = (best_correlation[i] << 16) / best_distortion[i];
+      ratio = (best_correlation[i] * (1 << 16)) / best_distortion[i];
     } else if (best_correlation[i] == 0) {
       ratio = 0;  // No correlation set result to zero.
     } else {