Ladybird: Don't push to history when loading through history navigation

Previously we were always pushing to history on the on_load_start
callback. Now we only do that if we are NOT navigating through the
history navigation (loading pages by going back/forward). This is what
the SerenityOS browser does:^)

Ladybird/Tab.cpp

@@ -83,7 +83,13 @@ Tab::Tab(BrowserWindow* window)
 
  QObject::connect(m_view, &WebContentView::load_started, [this](const URL& url) {
  m_location_edit->setText(url.to_string().characters());
- m_history.push(url, m_title.toUtf8().data());
+
+ // Don't add to history if back or forward is pressed
+ if (!m_is_history_navigation) {
+ m_history.push(url, m_title.toUtf8().data());
+ }
+ m_is_history_navigation = false;
+
  m_back_action->setEnabled(m_history.can_go_back());
  m_forward_action->setEnabled(m_history.can_go_forward());
  });
@@ -129,6 +135,7 @@ void Tab::back()
  if (!m_history.can_go_back())
  return;
 
+ m_is_history_navigation = true;
  m_history.go_back();
  view().load(m_history.current().url.to_string());
 }
@@ -138,6 +145,7 @@ void Tab::forward()
  if (!m_history.can_go_forward())
  return;
 
+ m_is_history_navigation = true;
  m_history.go_forward();
  view().load(m_history.current().url.to_string());
 }

Ladybird/Tab.h

@@ -64,4 +64,6 @@ public slots:
  OwnPtr<QAction> m_reload_action;
 
  int tab_index();
+
+ bool m_is_history_navigation { false };
 };