Make CompositeEditCommand::insertNodeAt() not to use Position::deprecatedEditingOffset()
Make CompositeEditCommand::insertNodeAt() not to use Position::deprecatedEditingOffset()

This patch replaces |Position::deprecatedEditingOffset()| call in
|CompositeEditCommand::insertNodeAt()| by |Position::offsetInContainerNode()|,
since we call |deprecatedEditingOffset()| for |OffsetInAnchor| type position
object from |Position::parentAnchoredEquivalent()| to avoid using legacy code
for improving code health.

This patch is a preparation of getting rid of legacy editing position.

BUG=513114
TEST=n/a; no behavior changes

Review URL: https://codereview.chromium.org/1264093002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@199783 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk