add flag to stage concat44 virtual change

Change-Id: Ibfccaaa9030b8698bfe5c2652e500b6375abcf12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2137821Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756934}

skia/config/SkUserConfig.h

@@ -211,6 +211,10 @@ SK_API void SkDebugf_FileLine(const char* file,
 // Staging for lowp::bilerp_clamp_8888, and for planned misc. others.
 #define SK_DISABLE_LOWP_BILERP_CLAMP_CLAMP_STAGE
 
+#ifndef SK_SUPPORT_LEGACY_DIDCONCAT44
+#define SK_SUPPORT_LEGACY_DIDCONCAT44
+#endif
+
 ///////////////////////// Imported from BUILD.gn and skia_common.gypi
 
 /* In some places Skia can use static initializers for global initialization,