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}
static bool ExecuteJustifyRight(LocalFrame& frame,
                                Event*,
                                EditorCommandSource source,
                                const String&) {
  return ExecuteApplyParagraphStyle(frame, source,
                                    InputEvent::InputType::kFormatJustifyRight,
                                    CSSPropertyTextAlign, "right");
}

static bool ExecuteJustifyRight(LocalFrame& frame,
                                Event*,
                                EditorCommandSource source,
                                const String&) {
  return ExecuteApplyParagraphStyle(frame, source,
                                    InputEvent::InputType::kFormatJustifyRight,
                                    CSSPropertyTextAlign, "right");
}
