I'm guessing that the reason you're doing this is because there isn't a way for one extension (JavaScriptQuickEdit) to call directly into another extension (JavaScriptCodeHints), which is an unfortunate limitation of our current extensibility mechanism. But I'm leery of adding public functionality like this into a core class like Editor, especially since the way this is set up, it won't generalize at all (e.g., if we had some other kind of "jump to definition" functionality for other languages in the future--e.g. going from an ID in a CSS selector to the HTML tag with that ID).

So maybe what we should do is make "Jump to Definition" actually be a command that's defined in the core, and have it rely on some `findDefinition()` function; that function in turn would delegate to providers that can be plugged in by language-specific extensions (where each provider would look at the current editor's mode to figure out if it applied--similar to how we do other language-specific providers).