RFR: 8343398: Add reducedData preference [v7]

[Kevin Rushforth]

On Wed, 18 Dec 2024 20:52:59 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> The `reducedData` preference instructs applications to minimize internet traffic, as users might be on a metered network or a limited data plan.
>> 
>> This corresponds to the following OS settings:
>> 
>> Windows: Settings -> Network and Internet -> Ethernet/WiFi -> Metered connection
>> macOS: Settings -> Network -> Ethernet/WiFi -> Network Settings -> Low data mode
>> Ubuntu: Settings -> Network -> Wired/WiFi -> Metered connection
>> 
>> Change notifications work consistently on Windows and macOS. On my Ubuntu 24 system, the GIO `network-changed` signal is not sent when I only toggle the "metered connection" flag in network settings (and there's no signal specifically for low-data mode). The new value is only picked up when the connection changes by coming offline or going online.
>
> Michael Strauß has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - typo
>  - store the app delegate reference in MacApplication

Our CI headful test build passed on macOS and Linux (I'll need to run Windows manually later), so the problem is fixed (the other Robot color mismatch test failures were unrelated, and fixed by rebooting the macOS systems in question).

I don't have access to Windows or Linux system where I can turn on the metering option, so I can't test if the notification works. Maybe someone else can?

I'll review the code tomorrow.

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PR Comment: https://git.openjdk.org/jfx/pull/1656#issuecomment-2552415742