Make ResourceLoader::makeComment a public static method

ResourceLoader::makeComment takes a block of text of converts it into a
/* multi-line comment block */ that is safe for inclusion in JavaScript and CSS
source code. There is no reason for the method to be protected, since it is
generic, useful, and free of side-effects.

Change-Id: Ibe45256eddee2ad30d19adcb2f1c0b0d5578e650