This reduces the number of `.cpp` files that need to be recompiled when one of the below header files changes as follows: Painting/Command.h: 1030 -> 61 Painting/DisplayList.h: 1030 -> 60 Painting/DisplayListRecorder.h: 557 -> 59
This will be used to differentiate between serialization for resolved style (i.e window.getComputedStyle()) and serialization for all other purposes.