cros: Add AppList mouse press autocomplete

Allow AppList autocomplete to complete suggestions
if SearchBoxView recieves a mouse press event.
Approved by UX.

Bug: 881465
Change-Id: I028b809150513567a45782fd176a8ca93ce532ca
Reviewed-on: https://chromium-review.googlesource.com/1211622Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Daniel Zhang <oxyflush@google.com>
Cr-Commit-Position: refs/heads/master@{#589327}

ash/app_list/views/search_box_view.cc

@@ -548,6 +548,8 @@ bool SearchBoxView::HandleMouseEvent(views::Textfield* sender,
     return app_list_view_->HandleScroll(
         (&mouse_event)->AsMouseWheelEvent()->offset().y(), ui::ET_MOUSEWHEEL);
   }
+  if (mouse_event.type() == ui::ET_MOUSE_PRESSED)
+    AcceptAutocompleteText();
   return search_box::SearchBoxViewBase::HandleMouseEvent(sender, mouse_event);
 }