Move undo window above the text that it refers to

Bug: b/166339813
Change-Id: Icf220bf8446cc9e6c761607dd99a9b918e4909fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377526
Auto-Submit: John Palmer <jopalmer@chromium.org>
Reviewed-by: My Nguyen <myy@chromium.org>
Reviewed-by: Keith Lee <keithlee@chromium.org>
Commit-Queue: Keith Lee <keithlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801691}

chrome/browser/chromeos/input_method/ui/undo_window.cc

@@ -32,6 +32,7 @@ UndoWindow::UndoWindow(gfx::NativeView parent, AssistiveDelegate* delegate)
   set_parent_window(parent);
   set_margins(gfx::Insets());
 
+  SetArrow(views::BubbleBorder::Arrow::BOTTOM_LEFT);
   SetLayoutManager(std::make_unique<views::BoxLayout>(
       views::BoxLayout::Orientation::kHorizontal));
   AddUndoButton();