If you’re using Chrome Canary for your development work now you can find a asyc radio button next to the callstack when you stop on a breakpoint in the DevTools.
Enabling it adds the functions that triggered an asynchronous action that called in the end the function you’ve your breakpoint in.
The awesome about this is that when you encounter an error in your callback you no longer need to add a breakpoint to the function that does the request (or other async action like setTimeout for instance) and repeat the action again. If the async mode is enabled you can see the scope of the variables from the time that the request took place.
Some months ago I stopped using the Chrome Canary for development because it was very slow but seems like I’m giving it an extra shot from today.