RFR: 8187309: TreeCell must not change tree's data

[Michael Strauß]

On Wed, 2 Feb 2022 14:18:18 GMT, Jeanette Winzenburg <fastegal at openjdk.org> wrote:

> Issue was TreeView commit editing implementation violated the spec'ed mechanism:
> 
> - no default commit handler on TreeView
> - TreeCell modifying the data directly
> 
> Fix is to move the saving of the edited value from cell into a default commit handler in tree and set that handler in the constructor.
> 
> Added tests that failed/passed before/after the fix (along with a sanity test for default commit that passed also before). Also fixed a test bug (incorrect registration of custom commit handler, see [JDK-8280951)](https://bugs.openjdk.java.net/browse/JDK-8280951) in TreeViewTest.test_rt_29650 to keep it passing.

Looks good to me.

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Marked as reviewed by mstrauss (Author).

PR: https://git.openjdk.java.net/jfx/pull/724