Add flag to opt into new pictureshader filtering

See https://skia-review.googlesource.com/c/skia/+/351505

Bug: skia:7650
Change-Id: I460c4791f610b5b4bff845238f87d3869a700d48
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615202Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
Cr-Commit-Position: refs/heads/master@{#841275}

skia/config/SkUserConfig.h

@@ -214,6 +214,10 @@ SK_API void SkDebugf_FileLine(const char* file,
 #define SK_DISABLE_REDUCE_OPLIST_SPLITTING
 #endif
 
+#ifndef SK_SUPPORT_LEGACY_INHERITED_PICTURE_SHADER_FILTER
+#define SK_SUPPORT_LEGACY_INHERITED_PICTURE_SHADER_FILTER
+#endif
+
 // Max. verb count for paths rendered by the edge-AA tessellating path renderer.
 #define GR_AA_TESSELLATOR_MAX_VERB_COUNT 100