Profiler: Add TimelineView widget and make the timeline cursor global

There's no longer a cursor in each process timeline, instead the parent
widget keeps track of it (along with the selection) and it all moves
in sync.

Userland/DevTools/Profiler/TimelineView.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGUI/Widget.h>
+
+namespace Profiler {
+
+class ProfileTimelineWidget;
+
+class TimelineView final : public GUI::Widget {
+    C_OBJECT(TimelineView);
+
+public:
+    virtual ~TimelineView() override;
+
+    bool is_selecting() const { return m_selecting; }
+    u64 select_start_time() const { return m_select_start_time; }
+    u64 select_end_time() const { return m_select_end_time; }
+    u64 hover_time() const { return m_hover_time; }
+
+    void set_selecting(Badge<ProfileTimelineWidget>, bool value)
+    {
+        m_selecting = value;
+        update();
+    }
+    void set_select_start_time(Badge<ProfileTimelineWidget>, u64 value)
+    {
+        m_select_start_time = value;
+        update();
+    }
+    void set_select_end_time(Badge<ProfileTimelineWidget>, u64 value)
+    {
+        m_select_end_time = value;
+        update();
+    }
+    void set_hover_time(Badge<ProfileTimelineWidget>, u64 value)
+    {
+        m_hover_time = value;
+        update();
+    }
+
+private:
+    TimelineView();
+
+    bool m_selecting { false };
+    u64 m_select_start_time { 0 };
+    u64 m_select_end_time { 0 };
+    u64 m_hover_time { 0 };
+};
+
+}