Implement Porter Duff XP with a blend table

include/gpu/GrContextOptions.h

Index: include/gpu/GrContextOptions.h
diff --git a/include/gpu/GrContextOptions.h b/include/gpu/GrContextOptions.h
index 686d6a9ac0eb5714dbe5f8cea01a72cfb4d3701e..dfb352b5078041e30cd27f0b4f6134fb0da02791 100644
--- a/include/gpu/GrContextOptions.h
+++ b/include/gpu/GrContextOptions.h
@@ -14,7 +14,8 @@ struct GrContextOptions {
     GrContextOptions()
         : fDrawPathToCompressedTexture(false)
         , fSuppressPrints(false)
-        , fMaxTextureSizeOverride(SK_MaxS32) {}
+        , fMaxTextureSizeOverride(SK_MaxS32)
+        , fSuppressDualSourceBlending(false) {}
 
     // EXPERIMENTAL
     // May be removed in the future, or may become standard depending
@@ -28,7 +29,8 @@ struct GrContextOptions {
         overrides can only reduce the feature set or limits, never increase them beyond the
         detected values. */
 
-    int fMaxTextureSizeOverride;
+    int  fMaxTextureSizeOverride;
+    bool fSuppressDualSourceBlending;
 };
 
 #endif