Make TypingCommand::insertText() to take SelectionInDOMTree instead of VisibleSelection

This patch makes |TypingCommand::insertText()| to take |SelectionInDOMTree|
instead of |VisibleSelection| to reduce usage of |VisibleSelection| for
improving code health.

BUG=657237
TEST=n/a

Review-Url: https://codereview.chromium.org/2733183002
Cr-Commit-Position: refs/heads/master@{#455368}
void Editor::respondToChangedSelection(
    const Position& oldSelectionStart,
    FrameSelection::SetSelectionOptions options) {
  spellChecker().respondToChangedSelection(oldSelectionStart, options);
  client().respondToChangedSelection(&frame(),
                                     frame()
                                         .selection()
                                         .selectionInDOMTree()
                                         .selectionTypeWithLegacyGranularity());
  setStartNewKillRingSequence(true);
}

void Editor::respondToChangedSelection(
    const Position& oldSelectionStart,
    FrameSelection::SetSelectionOptions options) {
  spellChecker().respondToChangedSelection(oldSelectionStart, options);
  client().respondToChangedSelection(&frame(),
                                     frame()
                                         .selection()
                                         .selectionInDOMTree()
                                         .selectionTypeWithLegacyGranularity());
  setStartNewKillRingSequence(true);
}
