Custom TimeArea Ruller Unity3d

How to create TimeArea the same as seen in Animation Window? Few reflections and voila.

  
    if (__timeAreaW == null) {
                                __timeAreaW = new TimeAreaW (false);

                                
                                __timeAreaW.hSlider = true;
                                __timeAreaW.vSlider = false;
                                __timeAreaW.vRangeLocked = true;
                                __timeAreaW.hRangeMin = 0f;
                                //__timeAreaW.hRangeMax=3f;

                                __timeAreaW.margin = 0f;
                                
                                __timeAreaW.scaleWithWindow = true;
                            
                                //__timeAreaW.ignoreScrollWheelUntilClicked = false;
                                if(__sequence!=null)
                                    __timeAreaW.hTicks.SetTickModulosForFrameRate (__sequence.frameRate);
                                else
                                    __timeAreaW.hTicks.SetTickModulosForFrameRate (30);

                                this.Repaint ();
            
                                
            
                        }

Source:

Custom Time Line Multi Selection Slider Handles - Unity3d

Great news that Unity reveal the code of new UI. But why they didn't reveal source of Editor/Inspector Components?. At least why they not remove those fucken internal and sealed from code, so we can use , AvatarPreview, AnimationTimeLine .... without doing lot of Reflection mambo jumbo.????

https://youtu.be/CAV_faETDvA?t=458

Use it like this:
EditorGUILayoutEx.CustomTimeLine (ref eventTimeValues,ref eventTimeValuesPrev, ref displayNames, ref eventTimeValuesSelected,-1, onAdd,oDelete,onClose,onEdit,onDragEnd ); Source: