Per the answers to this question, I closed Chrome from the taskbar, ensured there were no chrome.exe entries in Task Manager, opened C:\Users\myusername\AppData\Local\Google\Chrome\User Data\Default\Preferences
in Notepad++, removed the ,"window_placement":{...}
portion, saved, and reopened Chrome. There was no change in the defaults. I also tried modifying the settings instead of removing them altogether, but they just changed back when I opened Chrome again. I suspect something's changed in the past six years -- the settings have to be stored somewhere.
(I don't even know how it got changed to a tiny window way off-screen to the top-right in the first place. It was like that when I opened it, and I hadn't restarted since before the last time I opened Chrome the night before.)
chrome --window-position=x,y --window-size=w,h