Move back to using Chrome on OSX closes #2043

This moves back to using Chrome on OSX but making it obvious that it's Chrome to avoid any user issues with running Chrome itself. This also includes a more general refactoring of the browser launching code, as it had gotten a little convoluted after various revisions. This should be a bit more maintainable and portable.
> Oh, I see, we run it as an app on Linux. To make this distinction clearer, I might make app a boolean flag on addDefaultChromeArgs, at which point your comment here makes more sense.

Yeah I think if we did that we'd need to call it something other than addDefaultChromeArgs, but the idea is for that method to add common stuff while the OS-specific code customizes any commands as necessary.



> Also, rather than having it be addDefaultChromeArgs, I might make it buildChromeCommand and have it take care of finding the chrome executable from amongst all possible paths.

The tricky part there is that then that call would have to do custom stuff for each OS -- basically it would have to integrate much of the logic in WindowsBrowser, OSXBrowser, etc. To me it's nice to have those as separate files to avoid the mental clutter of worrying about the other OSes when you're typically only focused on one.