I would ask you to open up your task manager and try picking the largest-in-memory Chrome task and kill it, then see if you still think they are completely isolated. I agree with your point, but give it a shot.
That is chrome itself...of course closing the parent process of a bunch of processes that are tied to it and that it monitors is going to close them all.
I've used the Chrome task manager to kill tabs. There is one process in there that's just called "Browser"--that's obviously the parent, and the UI won't let you kill it.
You might be referring to the OS task manager, but I don't use that--don't need to. I think the fact that Chrome has its own task manager is a killer feature.
I don't think that's really fair, the largest Chrome task in memory isn't a tab or extension. Yes I suppose it isn't perfectly isolated and if something happens to the main program task it will obviously cause problems but if a single page or extension crashes everything else lives on.
It's a perfectly fair point. The fact that the largest Chrome task by far is not a tab or extension at all, but is the core of Chrome itself, indicates that maybe - just maybe - Chrome isn't doing as good a job of keeping things isolated as it should. That process shouldn't be doing a whole lot beyond driving the UI and managing the lifecycles of its children.
The point is to isolate any code which renders HTML, plugins, etc., i.e., anything which processes untrusted external input, something which the main process does not do.