Add missing virtual functions for SkRectClipCheckBlitter

This CL is related to the issue that we tried to fix in
https://skia-review.googlesource.com/c/5078/

Specifically, SkARGB32_Blitter overrides blitAntiH2 and blitAntiV2 and
they're different from blitAntiRuns. Therefore, if
SkRectClipCheckBlitter does not override those two functions, we're
going to get different results in debug and release build.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5082

Change-Id: I7f9565d494f0a6c45ab5a06fbedb73ef233b9a1f
Reviewed-on: https://skia-review.googlesource.com/5082
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
diff --git a/src/core/SkScanPriv.h b/src/core/SkScanPriv.h
index af0a4cb..4c237e0 100644
--- a/src/core/SkScanPriv.h
+++ b/src/core/SkScanPriv.h
@@ -24,7 +24,7 @@
     SkRectClipBlitter   fRectBlitter;
     SkRgnClipBlitter    fRgnBlitter;
 #ifdef SK_DEBUG
-    // SkRectClipCheckBlitter fRectClipCheckBlitter;
+    SkRectClipCheckBlitter fRectClipCheckBlitter;
 #endif
     SkBlitter*          fBlitter;
     const SkIRect*      fClipRect;