Allow GMs ato be used as benchmarks. Make convex_poly_clip opt in.

bench/SkBenchmark.h

Index: bench/SkBenchmark.h
diff --git a/bench/SkBenchmark.h b/bench/SkBenchmark.h
index bf44d2cc9702f295e9bdf7f52f80c2c86256bf23..b945a865167edd830e0caf8b049935547bb2d578 100644
--- a/bench/SkBenchmark.h
+++ b/bench/SkBenchmark.h
@@ -13,9 +13,13 @@
 #include "SkString.h"
 #include "SkTRegistry.h"
 
-#define DEF_BENCH(code) \
-static SkBenchmark* SK_MACRO_APPEND_LINE(F_)() { code; } \
-static BenchRegistry SK_MACRO_APPEND_LINE(R_)(SK_MACRO_APPEND_LINE(F_));
+#define DEF_BENCH(code)                                                 \
+namespace {                                                             \
+class SK_MACRO_APPEND_LINE(F_CLASS) : public SkBenchmarkFactory {       \
+    virtual SkBenchmark* operator()() const SK_OVERRIDE { code; }       \
+} SK_MACRO_APPEND_LINE(g_F_);                                           \
+BenchRegistry SK_MACRO_APPEND_LINE(g_R_)(&SK_MACRO_APPEND_LINE(g_F_));  \
+}
 
 /*
  *  With the above macros, you can register benches as follows (at the bottom
@@ -132,6 +136,11 @@ private:
     typedef SkRefCnt INHERITED;
 };
 
-typedef SkTRegistry<SkBenchmark*(*)()> BenchRegistry;
+class SkBenchmarkFactory : public SkRefCnt {
+public:
+    virtual SkBenchmark* operator()() const = 0;
+};
+
+typedef SkTRegistry<SkBenchmarkFactory*> BenchRegistry;
 
 #endif