Fix spellchecker updating of marker ranges spanning multiple elements.
The optimization made in Blink r187820 (https://crrev.com/828293002)
completely failed to take into account the case where the start and
end position spanned multiple nodes.
With EphemeralRange since then introduced, fix by switching to it.
For the original test optimized for (blink_perf.dom:textarea-edit),
local testing with chrome-release shows no degradation in performance
either.
R=yosin
BUG=579151
Review URL: https://codereview.chromium.org/1615963004
Cr-Commit-Position: refs/heads/master@{#370929}
2 files changed
