RFR: 8181084: JavaFX show big icons in system menu on macOS with Retina display [v6]

[Paul]

> I hit on JDK-8181084 while making some changes to Scene Builder, so I decided to investigate.
> 
> Please note: I have not done any Objective-C or MacOS development before. So I would really like some feedback from someone else who knows this stuff better.
> 
> Anyway, after some googling, I discovered that MacOS uses points values for measurements and not pixels, so the actual fix for this issue was this block in `GlassMenu.m`:-
> 
> 
>             if ((sx > 1) && (sy > 1) && (width > 1) && (height > 1)) {
>                 NSSize imgSize = {width / sx, height / sy};
>                 [image setSize: imgSize];
>             }
> 
> 
> The rest of the changes were needed in order to get the `scaleX` and `scaleY` values down from `PixelUtils.java` into `GlassMenu.m`.
> 
> Before this fix:-
> 
> <img width="239" alt="Screenshot 2022-02-26 at 22 16 30" src="https://user-images.githubusercontent.com/437990/155880981-92163087-696b-4442-b047-845c276deb27.png">
> 
> After this fix:-
> 
> <img width="218" alt="Screenshot 2022-02-26 at 22 18 17" src="https://user-images.githubusercontent.com/437990/155880985-6bff0a06-9aee-4db2-b696-64730b0a6feb.png">

Paul has updated the pull request incrementally with one additional commit since the last revision:

  Minor refactoring and code cleanup based on review feedback.

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/743/files
  - new: https://git.openjdk.org/jfx/pull/743/files/90971eeb..5c428549

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=743&range=05
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=743&range=04-05

  Stats: 64 lines in 6 files changed: 29 ins; 18 del; 17 mod
  Patch: https://git.openjdk.org/jfx/pull/743.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/743/head:pull/743

PR: https://git.openjdk.org/jfx/pull/743