The original implementation of `HTMLOptionElement::Text` is recursive,
and the program may run out of stack space for a sufficiently large
number of iterations. The patch switches to an iterative implementation,
with `TreeIterator`.
Note that, instead of the usual `while let Some(node) = iterator.next()`
approach, we use `while let Some(node) = iterator.peek()` with the newly
added `TreeIterator::peek` function. This is because the choice of the
next node depends on some checks performed inside the `while` block,
whereas the `next` function determines the next node before entering the
block.
Moreover, the `TreeIterator::peek` function is added, instead of
wrapping the iterator into `Peekable`. This is because we will lose
access to the `TreeIterator::next_skipping_children` function if we wrap
it into `Peekable`.
Testing: This refactoring has to pass the existing tests.
Fixes: #36959
Signed-off-by: Kingsley Yung <kingsley@kkoyung.dev>
be7efc94a3