Make Editor::changeSelectionAfterCommand take SelectionInDOMTree

Now that changing selection no longer requires layout, there is no
need to pass a canonicalized selection to changeSelectionAfterCommand
at the end of an editing command.

Hence, this patch makes the above mentioned function take a
SelectionInDOMTree instead.

BUG=657237
TEST=n/a; no behavior change

Review-Url: https://codereview.chromium.org/2720063002
Cr-Commit-Position: refs/heads/master@{#453795}
2 files changed