remove code from (dead) SK_SUPPORT_LEGACY_PIXELREF_UNFLATTENABLE flag

Source/platform/graphics/LazyDecodingPixelRef.h

Index: Source/platform/graphics/LazyDecodingPixelRef.h
diff --git a/Source/platform/graphics/LazyDecodingPixelRef.h b/Source/platform/graphics/LazyDecodingPixelRef.h
index a48bf6f8fa1aaa6566279847929688145aeb9ac8..6a0baa55dee768e00201041a277cb94e72efe260 100644
--- a/Source/platform/graphics/LazyDecodingPixelRef.h
+++ b/Source/platform/graphics/LazyDecodingPixelRef.h
@@ -50,10 +50,6 @@ public:
     LazyDecodingPixelRef(const SkImageInfo&, PassRefPtr<ImageFrameGenerator>, size_t index);
     virtual ~LazyDecodingPixelRef();
 
-#ifdef SK_SUPPORT_LEGACY_PIXELREF_UNFLATTENABLE
-    SK_DECLARE_UNFLATTENABLE_OBJECT()
-#endif
-
     PassRefPtr<ImageFrameGenerator> frameGenerator() const { return m_frameGenerator; }
     size_t frameIndex() const { return m_frameIndex; }