What example does Johnny give to show that Dally is gallant?

In Chapter 5, Johnny describes how he once saw Dally "gettin' picked up by the fuzz." Johnny says that Dally "kept real cool and calm the whole time." Dally also took the blame for the broken windows in the school, even though he knew that the windows were broken by Two-Bit. Dally, nonetheless, "just took the sentence without battin' an eye or even denyin' it." This, Johnny says, is "gallant."
The word "gallant" is often used to describe somebody who behaves chivalrously to somebody else, but it can also, more generally, be defined as meaning brave and courageous. Dally took a punishment to save someone else, and so "gallant" seems, in every sense of the word, a rather appropriate description.