Remove concept of child Widgets.

sky/engine/platform/scroll/Scrollbar.cpp

Index: sky/engine/platform/scroll/Scrollbar.cpp
diff --git a/sky/engine/platform/scroll/Scrollbar.cpp b/sky/engine/platform/scroll/Scrollbar.cpp
index 0e62bca7c23ab45608350b5574b62c40775b1ea9..09b4cf296421bc0dee69bd6c22fa13f116b67df8 100644
--- a/sky/engine/platform/scroll/Scrollbar.cpp
+++ b/sky/engine/platform/scroll/Scrollbar.cpp
@@ -26,11 +26,9 @@
 #include "config.h"
 #include "platform/scroll/Scrollbar.h"
 
-#include <algorithm>
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/PlatformGestureEvent.h"
 #include "platform/PlatformMouseEvent.h"
-#include "platform/FrameWidget.h"
 #include "platform/scroll/ScrollableArea.h"
 #include "platform/scroll/ScrollAnimator.h"
 #include "platform/scroll/Scrollbar.h"
@@ -88,12 +86,6 @@ Scrollbar::~Scrollbar()
     stopTimerIfNeeded();
 }
 
-void Scrollbar::removeFromParent()
-{
-    if (parent())
-        toFrameWidget(parent())->removeChild(this);
-}
-
 ScrollbarOverlayStyle Scrollbar::scrollbarOverlayStyle() const
 {
     return m_scrollableArea ? m_scrollableArea->scrollbarOverlayStyle() : ScrollbarOverlayStyleDefault;