RFR: 8272870: Add convenience factory methods for border and background [v3]

[Kevin Rushforth]

On Thu, 9 Sep 2021 23:43:29 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> Added convenience factory factory methods for Background and Border.
>
> Nir Lisker has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Removed whitespaces
>  - Added tests and doc updates

> Let's use the `Background` in all places where we refer the class name.

As a clarifying point, if it is capitalized, indicating an object of that type, it should use `{@code ... }`. I don't think all uses of `background` need to be `{@code Background}` (although that would be OK), so another possibility is to just capitalize the first occurrence and leave the others as lower-case?

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PR: https://git.openjdk.java.net/jfx/pull/610