TaskManager table's default sort should show the browser process at the top.
We have to ensure that the task manager by default (without any sorting)
shows the browser process task at the top of the list.
This CL also makes the RendererTasks match the old task manager behavior
by showing zeros for their network usage instead of N/As even when no
network bytes have been reported for them.
R=nick@chromium.org
BUG=523992
Review URL: https://codereview.chromium.org/
1322043003
Cr-Commit-Position: refs/heads/master@{#346950}