Add flag for filterquality in flutter

Change-Id: I8612d58efcfac82b7924c680fd8fa91b6d48614f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/426956
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

gn/flutter_defines.gni

@@ -20,6 +20,7 @@ flutter_defines = [
   "SK_DISABLE_LOWP_RASTER_PIPELINE",
   "SK_FORCE_RASTER_PIPELINE_BLITTER",
   "SK_SUPPORT_LEGACY_GETBLENDMODE",
+  "SK_SUPPORT_LEGACY_SETFILTERQUALITY",
 ]
 
 if (!is_fuchsia) {

include/core/SkPaint.h

@@ -26,7 +26,9 @@ class SkPathEffect;
 class SkShader;
 
 // Move to clients when they are ready -- aid in deprecating the enum
+#ifndef SK_SUPPORT_LEGACY_SETFILTERQUALITY
 #define SK_SUPPORT_LEGACY_SETFILTERQUALITY
+#endif
 
 /** \class SkPaint
     SkPaint controls options applied when drawing. SkPaint collects all