Seeing that GLaDOS isn't slouching off, Chell moves to the upper area with the light bridge. She peers around the test chamber, knowing that it has a use. But what is it to be used for?

She sees the other receptor for the laser and realizes that the light bridge and the gravity emitters could be used in conjunction to aim the laser into into it. With her portal gun, she creates an opening for the light bridge to jut across the room right by the second laser receptor.

GLaDOS had designed this test, so she would know what to do. No need to ping her, she hoped.