I imaged the device with R65-10309.0.0 and a chrome build (with symbols) @ 531333. I had the device setting on my desk at the login panel, and noticed the fans spinning. I wasn't doing anything, so I looked into cpu usage. This is a Pixel 1 with an external monitor hooked up (external @ 2560x1600).

When at the login cpu usage seems to hover around:

 3561 chronos   12  -8  422172 114984  83040 S  22.5  2.9   0:44.20 chrome
 3579 chronos   20   0 1077324 148512  49460 S  18.2  3.7   0:40.66 chrome
 3408 chronos   12  -8  663468 150520  77728 S  16.6  3.8   0:35.90 chrome
 3671 chronos   20   0 1029812 105332  37608 S   4.0  2.6   0:10.08 chrome

With unified:

 4812 chronos   12  -8  417632 110280  82532 R  34.2  2.8   0:09.28 chrome
 4665 chronos   12  -8  735296 150504  77780 R  26.6  3.8   0:10.66 chrome
 4830 chronos   20   0 1076768 150904  48776 S  17.9  3.8   0:11.18 chrome
 4903 chronos   20   0 1030836 114880  37268 S   4.7  2.9   0:04.24 chrome

once logged in (unified, with a single browser window with ntp and focus in the search box on the ntp):

 4665 chronos   12  -8  767336 175992  91628 S   7.6  4.4   0:20.72 chrome
 5152 chronos   20   0 1046860 117240  40808 S   6.6  2.9   0:05.04 chrome
 4812 chronos   12  -8  420100 115968  83132 S   2.0  2.9   0:16.18 chrome

In both cases, and especially unified, the login seems to consume an inordinate amount of CPU.