A few minutes ago I logged into a new site. I got the Save New Login dialog, and realized I needed to glance at a document in another app to check the spelling of something I wanted to include in the new login's description. I switched apps with ⌘⇥, checked the spelling, switched back to Chrome with ⌘⇥... and the Save New Login dialog was gone. I used Exposé, and then I moved every Chrome window off to the edge of the screen to make sure it wasn't just hiding at the bottom; no, it was gone.
That was odd. So I logged out of the site and tried again, and once again switched apps and back to Chrome. Same thing. Then I did it one more time, this time not actually switching apps, but just hitting ⌘⇥ while keeping my thumb held on ⌘, then pressed ⇧⇥ to re-choose Chrome, and released the keys. The app chooser disappeared, and so did the Save New Login dialog. (I suppose technically, while choosing an app, you have already
switched apps, to Dock.)
But I wasn't just digging for bugs; I did actually want to save a login.
So I logged out and back in one more time and saved the login. Then the previous Save New Login dialog I'd tested, with the unedited description, popped up! I dismissed it with Cancel, and the window before that, with the corrected spelling, popped up. I dismissed with Cancel, and finally the first window, with the misspelling, popped up. So apparently there was a stack of Save New Login dialogs that were hidden but waiting.
I'd call this a bug.