Use multimap to handle packets logged at the same time in the event log analyzer.
Use multimap to handle packets logged at the same time in the event log analyzer.

BUG=None

Review-Url: https://codereview.webrtc.org/2832773002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#17782}

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