WebKit does not follow HTML5 spellcheck attribute logic for words split by spans
"For text that is part of text or CDATA nodes, the element with which the text
is associated is the element that is the immediate parent of the start of the
word, sentence, or other piece of text. For text in attributes, it is the
element with which the attribute is associated. For text in text fields, it is
the relevant input or textarea element."
See test case.
Created attachment 29987 [details]