Revert of Remove RenderLayer::collectFragments.

sky/engine/core/rendering/LayerFragment.h

Index: sky/engine/core/rendering/LayerFragment.h
diff --git a/sky/engine/core/rendering/LayerFragment.h b/sky/engine/core/rendering/LayerFragment.h
index be5abd9dfeae6711c47ecc70a05199a175c0e685..c482e026461902adf9aad05e38dfb3e01ae63744 100644
--- a/sky/engine/core/rendering/LayerFragment.h
+++ b/sky/engine/core/rendering/LayerFragment.h
@@ -38,6 +38,29 @@
     {
     }
 
+    void setRects(const LayoutRect& bounds, const ClipRect& background, const ClipRect& foreground, const ClipRect& outline)
+    {
+        layerBounds = bounds;
+        backgroundRect = background;
+        foregroundRect = foreground;
+        outlineRect = outline;
+    }
+
+    void moveBy(const LayoutPoint& offset)
+    {
+        layerBounds.moveBy(offset);
+        backgroundRect.moveBy(offset);
+        foregroundRect.moveBy(offset);
+        outlineRect.moveBy(offset);
+    }
+
+    void intersect(const LayoutRect& rect)
+    {
+        backgroundRect.intersect(rect);
+        foregroundRect.intersect(rect);
+        outlineRect.intersect(rect);
+    }
+
     bool shouldPaintContent;
     LayoutRect layerBounds;
     ClipRect backgroundRect;