for record-dc%', record initial configuration after each erase'

Closes PR 12460

original commit: 1c6378451798d2e230d841d0f8d3afc9b4c078d3

collects/tests/gracket/record-dc.rkt

@@ -0,0 +1,59 @@
+#lang racket/base
+(require racket/class
+         racket/draw
+         racket/draw/private/record-dc)
+
+(define bm1 (make-bitmap 100 100))
+(define bm2 (make-bitmap 100 100))
+(define bm3 (make-bitmap 100 100))
+
+(define dc1 (make-object bitmap-dc% bm1))
+(define dc2 (make-object (record-dc-mixin bitmap-dc%) bm2))
+(define dc3 (make-object bitmap-dc% bm3))
+
+(define (config dc)
+  (send dc set-origin 2 3)
+  (send dc set-scale 1.1 0.9)
+  (send dc set-rotation 0.1)
+  (send dc set-initial-matrix '#(1.0 -0.1 0.1 1.0 1.0 2.0))
+  (send dc set-pen "red" 2 'solid)
+  (send dc set-brush "blue" 'solid)
+  (send dc set-font (make-font #:size 32))
+  (send dc set-smoothing 'smoothed)
+  (send dc set-text-mode 'solid)
+  (send dc set-alpha 0.8)
+  (send dc set-clipping-rect 5 5 95 95))
+
+(define (draw dc)
+  (send dc draw-ellipse 2 2 100 100)
+  (send dc draw-text "Hello" 10 10))
+
+(define (get-bytes bm)
+  (define w (send bm get-width))
+  (define h (send bm get-height))
+  (define bstr (make-bytes (* 4 w h)))
+  (send bm get-argb-pixels 0 0 w h bstr)
+  bstr)
+
+(config dc1)
+(draw dc1)
+
+(define pre-bytes (get-bytes bm1))
+
+(config dc2)
+(send dc2 erase)
+(draw dc2)
+
+(define middle-bytes (get-bytes bm2))
+
+(define cms (send dc2 get-recorded-command))
+
+(cms dc3)
+
+(define post-bytes (get-bytes bm3))
+
+(unless (equal? pre-bytes middle-bytes)
+  (error "middle != pre"))
+
+(unless (equal? pre-bytes post-bytes)
+  (error "post != pre"))