Worth noting that with a modification like that, it looks like it actually gives extra space for landing, not less. So that piece probably isn't a factor at all.
Runway 28L at SFO is 10,800 feet long in its current configuration. The spec for the 777 is 5,800 feet of runway for landing[1]. There is obviously a fair amount of weight, wind dependency in determining the minimum required length, but the runway was almost 100% longer than was necessary.
[1] http://www.ana.co.jp/eng/aboutana/corporate/galleryclassi/19...