RFR: 8286552: TextFormatter: UpdateValue/UpdateText is called, when no ValueConverter is set [v2]

[Marius Hanl]

> A common reason for using the `TextFormatter` is the need for a `filter`.
> Therefore, the following constructor is typically used:
> `public TextFormatter(@NamedArg("filter") UnaryOperator<Change> filter) { ... }`
> 
> With that, no `valueConverter` is set in the `TextFormatter`.
> 
> When a `TextField` will commit his value, `TextFormatter.updateValue(...)` is called.
> Since `valueConverter` is null, an NPE is thrown and catched inside it and `TextFormatter.updateText()` is called  (which will call `TextInputControl.updateText(...)`), which won't do anything either since `valueConverter` is still not set (=null).
> 
> A minor improvement here is to just skip `TextFormatter.updateValue(...)` and therefore `TextFormatter.updateText()` (-> `TextInputControl.updateText(...)`), since this methods won't do anything without a `valueConverter`.
> With that change, no exception (NPE) is thrown and catched, and therefore also exception breakpoints are not called (can be annoying ;)).
> This will also slightly increase the performance, as throwing exceptions is a (minor) bottleneck.
> 
> Added tests for all `TextFormatter` functionalities, which pass before and after.

Marius Hanl has updated the pull request incrementally with one additional commit since the last revision:

  8286552: Added space and revert typo fix

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

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/794/files
  - new: https://git.openjdk.java.net/jfx/pull/794/files/a171c370..bb157725

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=794&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=794&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/794.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/794/head:pull/794

PR: https://git.openjdk.java.net/jfx/pull/794