Add SK_SUPPORT_LEGACY_AA_CHOICE

Change-Id: Ic70101aa4d68e82dd77aaaa85a20dae95be39a08
Reviewed-on: https://chromium-review.googlesource.com/725820Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510114}

skia/config/SkUserConfig.h

@@ -228,6 +228,10 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_COLOR_SPACE_XFORM_LEGACY_PIPELINE
 #endif
 
+#ifndef SK_SUPPORT_LEGACY_AA_CHOICE
+#define SK_SUPPORT_LEGACY_AA_CHOICE
+#endif
+
 ///////////////////////// Imported from BUILD.gn and skia_common.gypi
 
 /* In some places Skia can use static initializers for global initialization,