Delete dead subset benches from nanobench

bench/subset/SubsetZoomBench.h

Index: bench/subset/SubsetZoomBench.h
diff --git a/bench/subset/SubsetZoomBench.h b/bench/subset/SubsetZoomBench.h
index 7fba4af94086bcd7d512aabe699eee5076605204..96e2eb1fc157bf0ff22a97e5c9de492ee2831e98 100644
--- a/bench/subset/SubsetZoomBench.h
+++ b/bench/subset/SubsetZoomBench.h
@@ -23,8 +23,7 @@ public:
     SubsetZoomBench(const SkString& path,
                     SkColorType colorType,
                     uint32_t subsetWidth,
-                    uint32_t subsetHeight,
-                    bool useCodec);
+                    uint32_t subsetHeight);
 
 protected:
     const char* onGetName() override;
@@ -36,7 +35,6 @@ private:
     SkColorType                   fColorType;
     const uint32_t                fSubsetWidth;
     const uint32_t                fSubsetHeight;
-    const bool                    fUseCodec;
     SkAutoTDelete<SkMemoryStream> fStream;
     typedef Benchmark INHERITED;
 };