WPT

fix: regression in serialization #8855

Job	Run time
1/6 chromedriver-headless	4m 42s
2/6 chromedriver-headless	3m 36s
3/6 chromedriver-headless	3m 49s
4/6 chromedriver-headless	3m 52s
5/6 chromedriver-headless	2m 50s
6/6 chromedriver-headless	3m 40s
1/6 chromedriver-headful	4m 44s
2/6 chromedriver-headful	3m 39s
3/6 chromedriver-headful	4m 18s
4/6 chromedriver-headful	3m 50s
5/6 chromedriver-headful	2m 59s
6/6 chromedriver-headful	3m 41s
1/6 mapper-headless	6m 40s
2/6 mapper-headless	6m 5s
3/6 mapper-headless	5m 56s
4/6 mapper-headless	5m 6s
5/6 mapper-headless	4m 17s
6/6 mapper-headless	5m 12s
[Required] WPT sink	1s
WPT report	0s
Update WPT expectations (if required)	0s
Commit updated expectations	0s
	1h 18m 57s

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