make blitAntiH2 virtual, to prep for larger change

src/core/SkBlitter.h

Index: src/core/SkBlitter.h
diff --git a/src/core/SkBlitter.h b/src/core/SkBlitter.h
index 2d4a0defbf8e77cebd9e770c473ba1aaacbfc0c2..8d9f7bcbedadce3dd9c0fe85e00a2a4765e223a7 100644
--- a/src/core/SkBlitter.h
+++ b/src/core/SkBlitter.h
@@ -8,6 +8,12 @@
 #ifndef SkBlitter_DEFINED
 #define SkBlitter_DEFINED
 
+#ifdef SK_SUPPORT_LEGACY_BLITANTIH2V2
+    #define SK_BLITANTIH2V2_VIRTUAL
+#else
+    #define SK_BLITANTIH2V2_VIRTUAL virtual
+#endif
+
 #include "SkBitmap.h"
 #include "SkBitmapProcShader.h"
 #include "SkMask.h"
@@ -54,7 +60,7 @@ public:
     virtual const SkBitmap* justAnOpaqueColor(uint32_t* value);
 
     // (x, y), (x + 1, y)
-    void blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) {
+    SK_BLITANTIH2V2_VIRTUAL void blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) {
         int16_t runs[3];
         uint8_t aa[2];
         
@@ -67,7 +73,7 @@ public:
     }
 
     // (x, y), (x, y + 1)
-    void blitAntiV2(int x, int y, U8CPU a0, U8CPU a1) {
+    SK_BLITANTIH2V2_VIRTUAL void blitAntiV2(int x, int y, U8CPU a0, U8CPU a1) {
         int16_t runs[2];
         uint8_t aa[1];