In this CL: - Don't insert a packet if we have explicitly cleared past it. - Added some logging to ExpandBufferSize. - Renamed IsContinuous to PotentialNewFrame. - Unittests updated/added for this new behavior. - Refactored TestPacketBuffer unittests. BUG=webrtc:5514 R=danilchap@webrtc.org, stefan@webrtc.org Review URL: https://codereview.webrtc.org/2399373002 . Cr-Commit-Position: refs/heads/master@{#14871}