* fix: 17453 don't lose text selection when contextmenu opens on another control
* fix: 17453 don't effect other callers and move the check to FocusChanged method
* Added failing AutoCompleteBox test.
* Make sure that flags are reset if exits early.
Wrap everything in a `try`...`finally` block so that they get reset even on exception.
Applying styling in the constructor isn't a good idea as demonstrated by #8549..
Instead apply styling when showing a window, or if it's needed call `ApplyStyling` manually, e.g. in unit tests.
Fixes#8549
And implement the functionality in the content controls themselves. `ContentControlMixin` was too complex and even with its complexity had bugs (such as in #2821). By moving the functionality to the content controls there is some repeated code but it's much more straightforward.
Nikita Tsukanov
Jan Karger ツ ☀
Steven Kirk
Robert Mutniański
AtomCrafty
Steven Kirk
Giuseppe Lippolis
Takoooooo
aguahombre
Kir-Antipov
Jeremy Koritzinsky
sdoroff