views::Textfield: Implement transpose editing command.

ui/views/controls/textfield/textfield.cc

Index: ui/views/controls/textfield/textfield.cc
diff --git a/ui/views/controls/textfield/textfield.cc b/ui/views/controls/textfield/textfield.cc
index 19e5c2ca689acbd6ab7cc7c045d7ef6bdd536c3e..0c29323db680d8575f88dc353a4915ac50f637d2 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -1488,6 +1488,9 @@ bool Textfield::IsTextEditCommandEnabled(ui::TextEditCommand command) const {
       return editable && !result.empty();
     case ui::TextEditCommand::SELECT_ALL:
       return !text().empty();
+    case ui::TextEditCommand::TRANSPOSE:
+      return editable && !model_->HasSelection() &&
+             !model_->HasCompositionText();
     case ui::TextEditCommand::MOVE_DOWN:
     case ui::TextEditCommand::MOVE_DOWN_AND_MODIFY_SELECTION:
     case ui::TextEditCommand::MOVE_PAGE_DOWN:
@@ -1681,6 +1684,9 @@ void Textfield::ExecuteTextEditCommand(ui::TextEditCommand command) {
     case ui::TextEditCommand::SELECT_ALL:
       SelectAll(false);
       break;
+    case ui::TextEditCommand::TRANSPOSE:
+      text_changed = cursor_changed = model_->Transpose();
+      break;
     case ui::TextEditCommand::MOVE_DOWN:
     case ui::TextEditCommand::MOVE_DOWN_AND_MODIFY_SELECTION:
     case ui::TextEditCommand::MOVE_PAGE_DOWN: