Annotate all Cocoa properties as nonatomic.

[jverkoey]

As best I can tell, none of the properties in the Cocoa directory truly rely on atomicity, so explicitly indicating this accomplishes three things:

1. Aligns with typical Objective-C convention of marking single-threaded properties nonatomic unless atomicity is explicitly required.
2. Removes any unnecessary overhead that may have been introduced by the Objective-C runtime in order to synthesize atomicity.
3. Refactoring of Document.h/m can follow typical conventions more closely.

Note, though, that it appears that the emulator does run on a background thread which in turn interacts with Cocoa views. This can lead to undefined behavior because Cocoa views aren't threadsafe. This can actually be seen in the logs with a warning for Main Thread Checker: UI API called on a background thread: -[NSWindow isVisible]. Ensuring that main-thread elements are only accessed via the main thread may be a reasonable follow-up.

Pre-work for #324.

[LIJI32]

Good catch, thanks!

As for main thread safety – I went through all these warnings at one point, fixing all of these with the exception of the one you just noted. The reason is that adding a a dispatch call in that use case created severe performance drops, so I was willing to take this thread-safety risk considering it's a bool property that doesn't change very frequently.

If you have a solution for this without using a dispatch, it'll be welcome; I hate this warning as much as you do :P

[jverkoey]

Filed #331 to track looking into the warning :)