Currently, BitrateProber does not scale higher than 2 Mbps to 6 Mbps. The actual
number is dependent on the size of the last packet. If a packet of around 250
bytes is used for probing, it fails above 2 Mbps.
BitrateProber now provides a recommendation on probe size instead of a
packet size. PacedSender utilizes this to decide on the number of packets
per probe. This enables BitrateProber to scale up-to higher bitrates.
Tests with chromoting show it stalls at about 10 Mbps (perhaps due to the
limitation on the simulation pipeline to deliver packets).
BUG=webrtc:6332
Review-Url: https://codereview.webrtc.org/2347023002
Cr-Commit-Position: refs/heads/master@{#14503}