gles/element: Take `src` into account #4902

Job	Run time
clippy-check	2m 30s
smithay-check-features	2m 57s
format	37s
smallvil-check	48s
check-msrv	1m 18s
smithay-tests	2m 34s
anvil-check-features	3m 58s
check-minimal	3m 17s
Documentation on Github Pages	4m 2s
WLCS: Core tests	2m 5s
WLCS: Output tests	3m 41s
WLCS: Pointer input tests	1m 14s
WLCS: Bad Buffer Test	6m 40s
	35m 41s

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