RFR: 8311805: Clean up ScrollPane: drop redundant initialiser, mark scroller final

[Sergey Bylokhov]

On Tue, 11 Jul 2023 11:44:15 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> A small clean-up of `awt.ScrollPane` code:
> 
> 1. Remove the redundant initialiser for `vs` in `layout` and move the declaration to where it's used. (One less `Dimension` object is created.)
> 2. Mark the `scroller` field of the `PeerFixer` class as `final`.
> 
> Perhaps, the  `PeerFixer` class could be `final` too.

Marked as reviewed by serb (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/14827#pullrequestreview-1524832856