add flag to stage new SkCanvas virtuals

See https://skia-review.googlesource.com/c/skia/+/263349

Change-Id: I04ee11072dd33ed5076a6b53ab580b4d5ed6b2f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1993626Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729925}

skia/config/SkUserConfig.h

@@ -215,6 +215,10 @@ SK_API void SkDebugf_FileLine(const char* file,
 #define SK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS
 #endif
 
+#ifndef SK_SUPPORT_LEGACY_CANVAS_MATRIX_VIRTUALS
+#define SK_SUPPORT_LEGACY_CANVAS_MATRIX_VIRTUALS
+#endif
+
 // Max. verb count for paths rendered by the edge-AA tessellating path renderer.
 #define GR_AA_TESSELLATOR_MAX_VERB_COUNT 100