RFR: 8313138: Scrollbar Keyboard enhancement [v7]

[Andy Goryachev]

> Adding alt-ctrl-LEFT/RIGHT/UP/DOWN (option-command-LEFT/RIGHT/UP/DOWN) key bindings to
> 
> - ListView
> - TreeView
> - TableView
> - TreeTableView
> 
> to support keyboard-only horizontal and vertical scrolling.  The main reason for the change is to improve accessibility.
> 
> **NOTE: For controls in right-to-left orientation, the direction of horizontal scrolling is reversed.**
> 
> As far as I can tell, these key combinations do not interfere with editing.
> 
> The proposed solution can be further optimized by adding a public method to the VirtualFlow class, something like
> 
> 
> public void horizontalUnitScroll(boolean right);
> public void verticalUnitScroll(boolean down);
> 
> 
> Q: Does this change require a CSR to explain the change in the controls' behavior?  We don't yet have the key bindings documented in /doc-files/behavior
> 
> Note:
> Jenkins headful test passed on all mac configurations, failed on all linux configurations (master branch failed also, so it is test issue), while windows configuration is not yet available.

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

  vertical scrolling tests

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1393/files
  - new: https://git.openjdk.org/jfx/pull/1393/files/859f7bbd..eeaa8d91

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1393&range=06
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1393&range=05-06

  Stats: 156 lines in 4 files changed: 146 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jfx/pull/1393.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1393/head:pull/1393

PR: https://git.openjdk.org/jfx/pull/1393