Originally ColorSpaces were only *partially* parsed on the worker-thread, to obtain an IR-format which was sent to the main-thread. This had the somewhat unfortunate side-effect of causing the majority of the (potentially heavy) ColorSpace parsing to happen on the main-thread.
Hence PR 4824 which, among other things, changed ColorSpaces to be *fully* parsed on the worker-thread with only RGB-data being sent to the main-thread.
While it thus originally was necessary to have `ColorSpace.{parseToIR, fromIR}` methods, to handle the worker/main-thread split, that's no longer the case and we can thus reduce all of the ColorSpace parsing to one method instead.
Currently, when parsing a ColorSpace, we call `ColorSpace.parseToIR` which parses the ColorSpace-data from the document and then creates the IR-format. We then, immediately, call `ColorSpace.fromIR` which parses the IR-format and then finally creates the actual ColorSpace.[1]
All-in-all, this leads to a fair amount of unnecessary indirection which also (in my opinion) makes the code less clear.
Obviously these changes are not really expected to have a significant effect on performance, especially with the recently added caching of ColorSpaces, however there'll now be strictly fewer function calls, less memory allocated, and overall less parsing required during ColorSpace-handling.
---
[1] For ICCBased ColorSpaces, given the validation necessary, this currently even leads to parsing an /Alternate ColorSpace *twice*.
ea6a0e4435