Reland: Implement Aura side of unified touch text selection for contents

ui/views/touchui/touch_editing_menu.cc

Index: ui/views/touchui/touch_editing_menu.cc
diff --git a/ui/views/touchui/touch_editing_menu.cc b/ui/views/touchui/touch_editing_menu.cc
index 7b2c5b61acfc2f7b82a2de626e8b7ab46d5922e8..b021aec1ba067d6922082c8f0a2d8b5f157d5a39 100644
--- a/ui/views/touchui/touch_editing_menu.cc
+++ b/ui/views/touchui/touch_editing_menu.cc
@@ -58,6 +58,11 @@ TouchEditingMenuView::TouchEditingMenuView(
   // menu is needed to be shown under the selection.
   gfx::Rect adjusted_anchor_rect(anchor_rect);
   int menu_width = GetPreferredSize().width();
+  // TODO(mfomitchev): This assumes that the handles are center-aligned to the
+  // |achor_rect| edges, which is not true. We should fix this, perhaps by
+  // passing down the cumulative width occupied by the handles within
+  // |anchor_rect| plus the handle image height instead of |handle_image_size|.
+  // Perhaps we should also allow for some minimum padding.
   if (menu_width > anchor_rect.width() - handle_image_size.width())
     adjusted_anchor_rect.Inset(0, 0, 0, -handle_image_size.height());
   SetAnchorRect(adjusted_anchor_rect);