RFR: 8354539: [macOS] ComboBox and Spinner disable system menu bar shortcuts

[Martin Fox]

The Mac platform code sends a KeyEvent into the scene graph and if the event is not consumed it gets sent on to the system menu. But ComboBox and Spinner always consume the original event and fire a copy which the system menu ignores.

In the past the platform code sent key events to the system menu even if the scene graph consumed them. This caused various bugs and was fixed in PR #1528 leading to this issue.

One could argue that a ComboBox or Spinner shouldn’t consume all key events but one could also argue that the system menu shouldn’t behave so differently from a standard MenuBar which will respond to any KeyEvent that reaches the top-level Scene no matter where it came from.

This PR installs an event dispatcher which forwards KEY_PRESSED events on to the platform so any event bubbling through the dispatch chain can trigger the system menu. The dispatcher is placed by the top-level (non-popup) Window such that it’s the last dispatcher encountered while bubbling.

In this PR once the key event reaches the GlassSystemMenu it passes the JavaFX key code and modifiers into the Mac platform code. This isn’t enough information to construct an NSEvent to pass to the main menu. Instead the code uses the code and modifiers to verify that the originating key down NSEvent (which it retained) should be sent on to NSApp.mainMenu.

(There are other ways this could work. GlassSystemMenu could take the KeyEvent and perform its own accelerator matching entirely inside Java. This would match the way the standard MenuBar finds accelerators instead of using Apple’s matching algorithm. This PR is the more conservative approach, basically just shifting the timing of system menu matching without changing how it’s done.)

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Commit messages:
 - Merge remote-tracking branch 'upstream/master' into sysmenuinplatform
 - Merge branch 'sysmenuinplatform' of ssh://github.com/beldenfox/jfx into sysmenuinplatform
 - Cleanup and fixed a popup redirection bug.
 - Validating the system menu key event against the originating NSEvent before sending it to NSApp.mainMenu.
 - Merge remote-tracking branch 'upstream/master' into sysmenuinplatform
 - System menu accelerators triggered in scene graph but resolved in platform code

Changes: https://git.openjdk.org/jfx/pull/1848/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1848&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354539
  Stats: 220 lines in 13 files changed: 168 ins; 30 del; 22 mod
  Patch: https://git.openjdk.org/jfx/pull/1848.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1848/head:pull/1848

PR: https://git.openjdk.org/jfx/pull/1848