Add new experimental API for rectangles with per-edge AA control

Also updates GM_draw_quad_set to use this API instead of the
bulk API on GrRenderTargetContext.

Bug: skia:8506
Change-Id: Ia342d83c509f9db69f06f01599c7041c98aabdb6
Reviewed-on: https://skia-review.googlesource.com/c/184488
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/include/utils/SkNWayCanvas.h b/include/utils/SkNWayCanvas.h
index 20714a6..09b071d 100644
--- a/include/utils/SkNWayCanvas.h
+++ b/include/utils/SkNWayCanvas.h
@@ -43,6 +43,7 @@
     void onDrawPaint(const SkPaint&) override;
     void onDrawPoints(PointMode, size_t count, const SkPoint pts[], const SkPaint&) override;
     void onDrawRect(const SkRect&, const SkPaint&) override;
+    void onDrawEdgeAARect(const SkRect&, SkCanvas::QuadAAFlags, SkColor, SkBlendMode) override;
     void onDrawRegion(const SkRegion&, const SkPaint&) override;
     void onDrawOval(const SkRect&, const SkPaint&) override;
     void onDrawArc(const SkRect&, SkScalar, SkScalar, bool, const SkPaint&) override;