Could the phrase "life passing before his eyes" be applied to the ending of To Kill a Mockingbird?
The phrase can be applied to the novel's end in several ways. Normally, for modern readers, the phrase has a negative connotation--the idea that someone is in a harrowing experience, sometimes right before death, and watches his life's experiences flash by. In To Kill a Mockingbird, however, the phrase can be connotatively positive or negative.
A positive interpretation of the phrase is that as Scout walks Boo Radley home after he has saved her and Jem's lives, she realizes that she is seeing her activities through Boo's eyes. As Jem, Scout, and Dill played through their summers near the Radley home, Boo had the opportunity to watch and admire the innocence and vivacity of children. Even though he was confined to the inner dreariness of his house, he saw the best in life pass before his eyes as he witnessed their antics.
On a more negative note, Boo watches the world go by without being a participant in it. He is simply a spectator, not someone who is truly living his life. Thus, life passes him by.