Roll engine to version b05efc204090f430387398d3c35589571a2fe16b (#14969)

* roll engine version in flutter/flutter to b05efc204090f430387398d3c35589571a2fe16b

* Fix analyzer warnings.

bin/internal/engine.version

-e133da723c603eb43c5bf03aeb27e79c06a50e0c
+b05efc204090f430387398d3c35589571a2fe16b

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

@@ -34,7 +34,7 @@ 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.
-class RenderProxyBox extends RenderBox with RenderObjectWithChildMixin<RenderBox>, RenderProxyBoxMixin {
+class RenderProxyBox extends RenderBox with RenderObjectWithChildMixin<RenderBox>, RenderProxyBoxMixin<RenderBox> {
   /// Creates a proxy render box.
   ///
   /// Proxy render boxes are rarely created directly because they simply proxy

packages/flutter/lib/src/widgets/overlay.dart

@@ -519,7 +519,7 @@ class _TheatreElement extends RenderObjectElement {
 // children of its primary subtree's stack can be moved to this object's list
 // of zombie children without changing their parent data objects.
 class _RenderTheatre extends RenderBox
-  with RenderObjectWithChildMixin<RenderStack>, RenderProxyBoxMixin,
+  with RenderObjectWithChildMixin<RenderStack>, RenderProxyBoxMixin<RenderBox>,
        ContainerRenderObjectMixin<RenderBox, StackParentData> {
 
   @override