UI stands for "user interface", which are the visualizations you see when interacting with a graphical shell. If something does not conform to the UI, that means it has its own UI that doesn't fit in.
I beg your pardon. UI stands for user interface, which is the way a user interfaces with an application. Yes, that includes appearance, but it is far from only that. The behaviors of menus, cursor interactions, focus, stacking, direction of elements, language, are all factors in a UI. Even vague things like "feel" which includes such nit picks as which elements of an interface respond to interaction while in the background, how a caret moves through a text field, what portions of a window are draggable. All of this and more is user interface.
Because that is what the browser is. The UI portion is peanuts, as proven by the fact that ONLY Google has screwed this up. Nobody else has.
And you listed other browsers using the same rendering engine as Chrome, so clearly the rendering engine has fuck all to do with the UI.
In Windows I don't have this problem. Every browser works pretty much like any other application, menus are where they should be, shortcuts are corrects, etc. The UI itself is an eyesore though and it's annoying to have just the one application that doesn't look right. It also makes it pretty much impossible to read some text in the UI due to conflicting colour schemes.
I'm pleased you see this much UI conformity in Windows. My experience on Windows is not the same, but I am also considering a much broader set of expectations (as listed above).
To clarify this entire conversation: we had a misunderstanding about what you meant by "UI", and diverged from there. Obviously Chrome looks out of place in some environments, because it has a fairly distinctive appearance of its own. Yes, I agree it can be annoying. But my point was that every current browser does unconventional things in their UI, because the UI toolkits available to them are too limited for the needs of a good browser interface. I hope we can agree that is the case as ell?