MouseWheelEventQueue sends scrollEnd right away when latching is disabled.

content/browser/renderer_host/input/mock_input_ack_handler.h

Index: content/browser/renderer_host/input/mock_input_ack_handler.h
diff --git a/content/browser/renderer_host/input/mock_input_ack_handler.h b/content/browser/renderer_host/input/mock_input_ack_handler.h
index cb390ae6934a46fcf71619b5273371a068d4afe2..4452f650523898ed731f867d7724a1ae7e995b0b 100644
--- a/content/browser/renderer_host/input/mock_input_ack_handler.h
+++ b/content/browser/renderer_host/input/mock_input_ack_handler.h
@@ -55,6 +55,10 @@ class MockInputAckHandler : public InputAckHandler {
   }
   InputEventAckState ack_state() const { return ack_state_; }
 
+  InputEventAckState acked_wheel_event_state() const {
+    return acked_wheel_event_state_;
+  }
+
   blink::WebInputEvent::Type ack_event_type() const { return ack_event_type_; }
 
   const NativeWebKeyboardEvent& acked_keyboard_event() const {
@@ -80,6 +84,7 @@ class MockInputAckHandler : public InputAckHandler {
   bool unexpected_event_ack_called_;
   blink::WebInputEvent::Type ack_event_type_;
   InputEventAckState ack_state_;
+  InputEventAckState acked_wheel_event_state_;
   std::unique_ptr<NativeWebKeyboardEvent> acked_key_event_;
   blink::WebMouseWheelEvent acked_wheel_event_;
   TouchEventWithLatencyInfo acked_touch_event_;