I fail to pick up the relation. The Church Turing thesis is an unproveable statement arguing that a turing machine can compute every computable function. It also notes the equivalent ability in mu recursive functions and the lambda calculus.
Now correct me if I'm wrong. But "Every computable function" includes another Turing machine. If browser developers are insistent on turning the web browser into a sort of web virtual machine; then it stands to reason that a "operating system" running in the browser is just as legitimate as one in virtualbox or similar software.
Is the concept ridiculous? Probably. But time transforms all things. Many things that were once ridiculous are no longer so. I'm eager to see how things on this line of thought turn out.
I am saying that the church turing thesis is not a fact or theorem. It is an unprovable hypothesis, a belief whose inclusion in a deduction does not add any more to it unless the receiving party also agrees with it.
The other part is that the notion of an operating system is not typically tied to a turing machine. An operating system is essentially a set of libraries for any language with appropriate bindings. The language being an abstraction of the underlying machine. To show an equivalence between an OS and browser you list the properties of and operations on a browser and that of an operating system and show there is an isomorphism from one to the other.
Anyways I agree with your conclusion, just not with your argument route. As browsers increase in power they will be indistinguishable from the OS in terms of functionality they expose to the consuming language. The current OSs approach from the other end.
I think you're missing Unimpressive's point that if something can be run virtualized we don't cease to refer to it as an operating system. If Linux had been (perversely, ahistorically) developed as jslinux first before the bare-metal interfaces were implemented would it now be considered not-an-OS? Conversely would the act of porting it have blessed its status as an OS without regard to the presence of the same semantics and facilities in the browser version? I think if you're making this argument you're running against the tide of common _and_ academic usage, plenty of research OS projects have been tested on hardware simulators. Perhaps the easiest way to simplify this is to ask whether you can present any rule other than "browsers don't count" to distinguish the virtualized Linux case from the jslinux case.
The point being made is not that a browser is an OS, but that something using the facilities of a browser to implement all the operations and environment of an OS is... an OS. This seems almost like the duck typing versus strong typing approach - one view is that it's the behaviors that define the identity of something, the other is that it's the inheritance & implementation[].
[] Alternatively since it's April Fools, I'll argue that you're interrogating this from the wrong angle and presenting an essentialist view of OS-hood.
If it runs in the browser, it's not an operating system. Nice April 1 joke.