RFR: 8370612: Simplify implementation of dark theme

[Hannes Wallnöfer]

On Fri, 31 Oct 2025 22:48:45 GMT, Chen Liang <liach at openjdk.org> wrote:

> What is the purpose of the padding change? I see the padding is now narrower, but the bar is still thicker than in 25.

The button was just a bit large, both compared to nearby elements such as the filter input, and to other buttons in the UI such as the theme picker or copy-to-clipboard button. Now it's the same size as the other buttons (32 x 32 px). (Image button size is content + 2 * padding, so padding has to be adjusted to the image.) Using `px` as unit is also a bit more consistent with other buttons.

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PR Comment: https://git.openjdk.org/jdk/pull/28085#issuecomment-3479537630