Dynamically update feature pod rows based on available height for system tray

We now reduce the number of rows of FeaturePods based on the available height
for the system tray.
The number of rows can go down to 1, the maximum rows remain unchanged at 3.

Bug: 984367
Change-Id: Ia59afeecd357d62042d07ba15b3b40cdf90781ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704039
Reviewed-by: Tim Song <tengs@chromium.org>
Reviewed-by: Jenny Zhang <jennyz@chromium.org>
Commit-Queue: Ahmed Mehfooz <amehfooz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681073}