Investigate why css-style-declaration-modifications.html and inline-style-001.html times out

[nox]

Seems like there is something wrong going on with the loop of the third test.

servo/tests/wpt/web-platform-tests/css/cssom/css-style-declaration-modifications.html

Lines 45 to 47 in b211e45

	while (declaration.length > 0) {
	declaration.removeProperty(declaration.item(0));
	}

[nox]

Test inline-style-001.html times out for the same reason.