The new format for plot lines is PLOT <plot_no> <var_name>:<ssrc>@<alg_name> <time> <value>. The var_name is no longer prefixed by the context/tag (which most of the time was just the same as the test name.)
Update plot_dynamics.py script (which didn't work) to visualize the new BWE_TEST_LOGGING_PLOT lines.
BUG=webrtc:6621
Review-Url: https://codereview.webrtc.org/2456373002
Cr-Commit-Position: refs/heads/master@{#14983}