Dowden's explanation is: "The central motive of the speech is 'Come night, come Romeo.' Having invoked night to spread the curtain, Juliet says, with a thought of her own joyful wakefulness, 'Yonder sun may sleep' (wink having commonly this sense); and then she calls on Romeo to leap to her arms." He agreed with Warburton that "runaway's" means Phoebus or the sun. With the rest of them however he found difficulty in proving that it was well to call the sun a runaway when Juliet was complaining of its being slow. He tried however—with results remarkably hard to understand.
The result of trying a different sentence division, as instanced in Neilson's edition (1906) is that it has left on hand the following statement as a separate sentence.
Untalked of and unseen
Lovers can see to do their amorous rites,
And by their own beauties; etc.
Can anyone imagine Shakespeare tendering the piece of valuable information conveyed in these first two lines!
The sentence division of the First Folio is correct. It is from this standpoint that I have explained the passage. The Globe text is quite acceptable in this regard; but the "runaways'" of this edition should be changed to "runaway's."