LibWeb: Add internals.wheel() to simulate mouse wheel events

This function allows us to write tests for scrolling scenarios where
the events are processed by the EventHandler.

Userland/Libraries/LibWeb/Internals/Internals.cpp

@@ -83,6 +83,12 @@ void Internals::click(double x, double y)
     page.handle_mouseup({ x, y }, { x, y }, 1, 0, 0);
 }
 
+void Internals::wheel(double x, double y, double delta_x, double delta_y)
+{
+    auto& page = global_object().browsing_context()->page();
+    page.handle_mousewheel({ x, y }, { x, y }, 0, 0, 0, delta_x, delta_y);
+}
+
 WebIDL::ExceptionOr<bool> Internals::dispatch_user_activated_event(DOM::EventTarget& target, DOM::Event& event)
 {
     event.set_is_trusted(true);

Userland/Libraries/LibWeb/Internals/Internals.h

@@ -26,6 +26,7 @@ public:
     void commit_text();
 
     void click(double x, double y);
+    void wheel(double x, double y, double delta_x, double delta_y);
 
     WebIDL::ExceptionOr<bool> dispatch_user_activated_event(DOM::EventTarget&, DOM::Event& event);
 

Userland/Libraries/LibWeb/Internals/Internals.idl

@@ -11,6 +11,7 @@
     undefined commitText();
 
     undefined click(double x, double y);
+    undefined wheel(double x, double y, double deltaX, double deltaY);
 
     boolean dispatchUserActivatedEvent(EventTarget target, Event event);