add SK_LEGACY_SRGB_STAGE_CHOICE

TBR=fmalita@chromium.org

This will guard https://skia-review.googlesource.com/c/skia/+/165766.

Change-Id: I6cf70a5d2e0eab1698c534bf8ccf8fdc6f81e19a
Reviewed-on: https://chromium-review.googlesource.com/c/1305153Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603551}

skia/config/SkUserConfig.h

@@ -160,6 +160,8 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_SUPPORT_LEGACY_AAA_CHOICE
 #endif
 
+#define SK_LEGACY_SRGB_STAGE_CHOICE
+
 ///////////////////////// Imported from BUILD.gn and skia_common.gypi
 
 /* In some places Skia can use static initializers for global initialization,