Get rid of flat tree version of createVisibleSelection() taking one ePosition
This patch gets rid of flat tree version of |createVisibleSelection()| taking
one |Position| by replacing with |SelectionInDOMTree| version to reduce number
of overloads for improving code health.
BUG=
657237
TEST=n/a; no behavior changes
Committed:
https://crrev.com/7fffd89947118c4719ccfb7afceae7ca66d93f5b
Cr-Commit-Position: refs/heads/master@{#427280}