Don't use rtc::PacketTime explicitly, use implicit int64_t conversion

This is a step towards deleting the rtc::PacketTime class.

Bug: webrtc:9584
Change-Id: Iaae4dd05d398fc6ea67d63981277fb84859b5c21
Reviewed-on: https://chromium-review.googlesource.com/c/1313931
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Niels Möller <nisse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605285}
5 files changed