Ladybird: Floor the WebContentView viewport offset at 0, 0

This fixes an unpleasant visual glitch when resizing the window.
When the user makes our QAbstractScrollArea larger, the scroll bars can
end up with negative values, which we were happily forwarding to the
WebContent process and asking it to paint the whole page at an offset.

Ladybird/WebContentView.cpp

@@ -397,12 +397,12 @@ void WebContentView::focusOutEvent(QFocusEvent*)
 
 Gfx::IntPoint WebContentView::to_content(Gfx::IntPoint viewport_position) const
 {
-    return viewport_position.translated(horizontalScrollBar()->value(), verticalScrollBar()->value());
+    return viewport_position.translated(max(0, horizontalScrollBar()->value()), max(0, verticalScrollBar()->value()));
 }
 
 Gfx::IntPoint WebContentView::to_widget(Gfx::IntPoint content_position) const
 {
-    return content_position.translated(-horizontalScrollBar()->value(), -verticalScrollBar()->value());
+    return content_position.translated(-(max(0, horizontalScrollBar()->value())), -(max(0, verticalScrollBar()->value())));
 }
 
 void WebContentView::paintEvent(QPaintEvent*)
@@ -484,7 +484,7 @@ void WebContentView::update_viewport_rect()
 {
     auto scaled_width = int(viewport()->width() / m_inverse_pixel_scaling_ratio);
     auto scaled_height = int(viewport()->height() / m_inverse_pixel_scaling_ratio);
-    Gfx::IntRect rect(horizontalScrollBar()->value(), verticalScrollBar()->value(), scaled_width, scaled_height);
+    Gfx::IntRect rect(max(0, horizontalScrollBar()->value()), max(0, verticalScrollBar()->value()), scaled_width, scaled_height);
 
     set_viewport_rect(rect);
 
@@ -787,8 +787,8 @@ void WebContentView::notify_server_did_change_title(Badge<WebContentClient>, Dep
 
 void WebContentView::notify_server_did_request_scroll(Badge<WebContentClient>, i32 x_delta, i32 y_delta)
 {
-    horizontalScrollBar()->setValue(horizontalScrollBar()->value() + x_delta);
-    verticalScrollBar()->setValue(verticalScrollBar()->value() + y_delta);
+    horizontalScrollBar()->setValue(max(0, horizontalScrollBar()->value() + x_delta));
+    verticalScrollBar()->setValue(max(0, verticalScrollBar()->value() + y_delta));
 }
 
 void WebContentView::notify_server_did_request_scroll_to(Badge<WebContentClient>, Gfx::IntPoint scroll_position)