RFR: 8319925: CSS.BackgroundImage incorrectly uses double-checked locking

[Alexey Ivanov]

On Fri, 1 Dec 2023 06:31:00 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> CSS.BackgroundImage.getImage uses double-checked locking but the loadedImage field isn't declared as volatile. Without the volatile modifier, double-checked locking implementation is broken.

Based on my recent comment, the code needs updating.

Thanks @mrserb for catching another mistake.

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Changes requested by aivanov (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16917#pullrequestreview-1762509285