ui: Cleanup class/struct forward declarations

content/renderer/input/render_widget_input_handler.cc

Index: content/renderer/input/render_widget_input_handler.cc
diff --git a/content/renderer/input/render_widget_input_handler.cc b/content/renderer/input/render_widget_input_handler.cc
index 264072e85ae3582dc9a4ae9c7b61639eff3a3707..7bda81469a6109ed0195b7ced776154bb66acd66 100644
--- a/content/renderer/input/render_widget_input_handler.cc
+++ b/content/renderer/input/render_widget_input_handler.cc
@@ -405,8 +405,8 @@ void RenderWidgetInputHandler::HandleInputEvent(
   if ((dispatch_type == DISPATCH_TYPE_BLOCKING ||
        dispatch_type == DISPATCH_TYPE_BLOCKING_NOTIFY_MAIN)) {
     std::unique_ptr<InputEventAck> response(new InputEventAck(
-        input_event.type, ack_result, swap_latency_info,
-        std::move(event_overscroll),
+        InputEventAckSource::MAIN_THREAD, input_event.type, ack_result,
+        swap_latency_info, std::move(event_overscroll),
         ui::WebInputEventTraits::GetUniqueTouchEventId(input_event)));
     delegate_->OnInputEventAck(std::move(response));
   } else {