Missing default hardEdge clip for ClipRectLayer (#21826)

In my local tests, this should finally fix https://github.com/flutter/flutter/issues/21617

bin/internal/goldens.version

-da68caa0a261663858998e047c02560e94404e7a
+96ed11be7a52f9b8ace5af0a286d8d4415dbd78b

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

@@ -622,7 +622,7 @@ class ClipRectLayer extends ContainerLayer {
   ///
   /// The [clipRect] property must be non-null before the compositing phase of
   /// the pipeline.
-  ClipRectLayer({ this.clipRect, Clip clipBehavior = Clip.antiAlias }) :
+  ClipRectLayer({ this.clipRect, Clip clipBehavior = Clip.hardEdge }) :
         _clipBehavior = clipBehavior, assert(clipBehavior != null), assert(clipBehavior != Clip.none);
 
   /// The rectangle to clip in the parent's coordinate system.

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

@@ -385,7 +385,7 @@ class PaintingContext extends ClipContext {
   /// * `painter` is a callback that will paint with the [clipRect] applied. This
   ///   function calls the [painter] synchronously.
   /// * `clipBehavior` controls how the rectangle is clipped.
-  void pushClipRect(bool needsCompositing, Offset offset, Rect clipRect, PaintingContextCallback painter, {Clip clipBehavior = Clip.antiAlias}) {
+  void pushClipRect(bool needsCompositing, Offset offset, Rect clipRect, PaintingContextCallback painter, {Clip clipBehavior = Clip.hardEdge}) {
     final Rect offsetClipRect = clipRect.shift(offset);
     if (needsCompositing) {
       pushLayer(ClipRectLayer(clipRect: offsetClipRect, clipBehavior: clipBehavior), painter, offset, childPaintBounds: offsetClipRect);