Added missing include to fix waterfall compile error.
Added missing include to fix waterfall compile error.

Bots failue caused by https://codereview.webrtc.org/2517243005/

NOTRY=True
TBR=stefan@webrtc.org
BUG=webrtc:6638

Review-Url: https://codereview.webrtc.org/2544473002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#15318}

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