Move Editor::Transpose() out of Editor class

This patch moves |Editor::Transpose()| out of |Editor| class as preparation of
expanding it into |ExecutTranspose()| in "EditorCommand.cpp" to make |Editor|
class simpler for improving code health.

Following patch will expand |Transpose()| into |ExecutTranspose()|.

Bug: 672405
Change-Id: Icde253623f31813d2b4517c4da7d4798bd5fadf6
Reviewed-on: https://chromium-review.googlesource.com/583880
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#489518}
void Editor::ApplyStyle(StylePropertySet* style,
                        InputEvent::InputType input_type) {
  switch (GetFrame()
              .Selection()
              .ComputeVisibleSelectionInDOMTreeDeprecated()
              .GetSelectionType()) {
    case kNoSelection:
      break;
    case kCaretSelection:
      ComputeAndSetTypingStyle(style, input_type);
      break;
    case kRangeSelection:
      if (style) {
        DCHECK(GetFrame().GetDocument());
        ApplyStyleCommand::Create(*GetFrame().GetDocument(),
                                  EditingStyle::Create(style), input_type)
            ->Apply();
      }
      break;
  }
}

void Editor::ApplyStyle(StylePropertySet* style,
                        InputEvent::InputType input_type) {
  switch (GetFrame()
              .Selection()
              .ComputeVisibleSelectionInDOMTreeDeprecated()
              .GetSelectionType()) {
    case kNoSelection:
      break;
    case kCaretSelection:
      ComputeAndSetTypingStyle(style, input_type);
      break;
    case kRangeSelection:
      if (style) {
        DCHECK(GetFrame().GetDocument());
        ApplyStyleCommand::Create(*GetFrame().GetDocument(),
                                  EditingStyle::Create(style), input_type)
            ->Apply();
      }
      break;
  }
}
