In Chrome, Tools -> Developer Tools -> Elements tab. There are no line numbers next to the source code. Is there a way to toggle them on?
Don't know how useful it will be, but you can right click on the html element in the Elements tab, select "Copy as HTML" and paste the results in your favorite text editor. That will give you line numbers for the DOM as it exists at the point where you copy it.
Like the comments point out, this will not correspond to source line numbers.