Fix for left-shift of potentially negative values in NetEq.
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: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#15966}

TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc