Bug 913759 part 1: Treat buttonContent frames as block wrappers, so percent heights inside a button can resolve against button's height (minus focus border/padding). r=bz
Bug 913759 part 2: reftests for percent-sized content in a button. r=bz
Bug 915488 - Make CC participant's Root, Unroot and Unlink methods infallible. r=smaug