add flag to stage Skia API change

See https://skia-review.googlesource.com/c/skia/+/337719

Change-Id: I39edd57272ecd08c25999ffe2efe22c091a1b544
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2555899
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Cr-Commit-Position: refs/heads/master@{#830374}

skia/config/SkUserConfig.h

@@ -233,6 +233,10 @@ SK_API void SkDebugf_FileLine(const char* file,
 #define SK_SUPPORT_LEGACY_ADJUSTHQHEURISTIC
 #endif
 
+#ifndef SK_SUPPORT_LEGACY_SCALEPIXELS_PARAM
+#define SK_SUPPORT_LEGACY_SCALEPIXELS_PARAM
+#endif
+
 // Staging for lowp::bilerp_clamp_8888, and for planned misc. others.
 #define SK_DISABLE_LOWP_BILERP_CLAMP_CLAMP_STAGE