Some things Chrome includes that other browsers do not: Pepper, Native Client, Chrome Web Store, WebSQL (Safari might have that one too), a native PDF viewer, SwiftShader, etc.
(People of course disagree on which of those are bad and which are good.)
It's only in the Dartium branch so far, I believe - not in trunk Chromium or release Chrome. But yes, it's another controversial feature that Google is planning to bundle.
Interesting. I can't really tell how fast Chrome starts up, because it's starts in the background when my desktop environment loads and I'm on an SSD. But that would in fact be a good indicator for bloat.
(People of course disagree on which of those are bad and which are good.)