RFR: 8230809: HTMLEditor formatting lost when selecting all (CTRL-A)

[Ajit Ghaisas]

Bug : https://bugs.openjdk.java.net/browse/JDK-8230809

Root Cause :
Turned out to be a simpler issue than thought.
Atomicity check was missed while updating toolbar state (which in turn updates styles).

Fix :
Added the missed atomicity check at two places that handle text selection using keyboard keys.

Testing :
Added two system test cases. They fail without this fix and pass with it.

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Commit messages:
 - Fix_8230809

Changes: https://git.openjdk.java.net/jfx/pull/155/files
 Webrev: https://webrevs.openjdk.java.net/jfx/155/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8230809
  Stats: 115 lines in 2 files changed: 112 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jfx/pull/155.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/155/head:pull/155

PR: https://git.openjdk.java.net/jfx/pull/155