I can't speak to what chrome does, but usually there would be rollup patches to take advantage of, cutting down the number of patches to apply dramatically. E.g. To get from 23 to 76 you might only need to apply 23->25->75->76. This would be slightly less efficient than going directly both in terms of time patching and patch size, but not terribly so (one can assume most patches are decently disjoint). Most importantly, this keeps the total number of supported patches manageable.