Remove static initializer of GrProcessorSet::gEmpty

Change-Id: I9d4cb34c54458ad42a413f251d1018217de26b90
Reviewed-on: https://skia-review.googlesource.com/17206
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/GrProcessorSet.h b/src/gpu/GrProcessorSet.h
index b15da1e..b13175a 100644
--- a/src/gpu/GrProcessorSet.h
+++ b/src/gpu/GrProcessorSet.h
@@ -134,12 +134,11 @@
 
     bool isFinalized() const { return SkToBool(kFinalized_Flag & fFlags); }
 
-    static const GrProcessorSet& EmptySet() { return gEmpty; }
+    static const GrProcessorSet& EmptySet();
     static constexpr const Analysis EmptySetAnalysis() { return Analysis(Empty::kEmpty); }
 
 private:
     GrProcessorSet(Empty) : fXP((const GrXferProcessor*)nullptr), fFlags(kFinalized_Flag) {}
-    static const GrProcessorSet gEmpty;
 
     // This absurdly large limit allows Analysis and this to pack fields together.
     static constexpr int kMaxColorProcessors = UINT8_MAX;