RenderProxySliver (#45942)

packages/flutter/lib/rendering.dart

@@ -50,6 +50,7 @@ export 'src/rendering/paragraph.dart';
 export 'src/rendering/performance_overlay.dart';
 export 'src/rendering/platform_view.dart';
 export 'src/rendering/proxy_box.dart';
+export 'src/rendering/proxy_sliver.dart';
 export 'src/rendering/rotated_box.dart';
 export 'src/rendering/shifted_box.dart';
 export 'src/rendering/sliver.dart';

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -26,7 +26,7 @@ export 'package:flutter/gestures.dart' show
   PointerUpEvent,
   PointerCancelEvent;
 
-/// A base class for render objects that resemble their children.
+/// A base class for render boxes that resemble their children.
 ///
 /// A proxy box has a single child and simply mimics all the properties of that
 /// child by calling through to the child for each function in the render box
@@ -37,6 +37,11 @@ export 'package:flutter/gestures.dart' show
 /// the proxy box with its child. However, RenderProxyBox is a useful base class
 /// for render objects that wish to mimic most, but not all, of the properties
 /// of their child.
+///
+/// See also:
+///
+///  * [RenderProxySliver], a base class for render slivers that resemble their
+///    children.
 class RenderProxyBox extends RenderBox with RenderObjectWithChildMixin<RenderBox>, RenderProxyBoxMixin<RenderBox> {
   /// Creates a proxy render box.
   ///