added auto as default value for complexity

include/benchmark/benchmark_api.h

@@ -501,7 +501,7 @@ public:
 
   // Set the asymptotic computational complexity for the benchmark. If called
   // the asymptotic computational complexity will be shown on the output. 
-  Benchmark* Complexity(BigO complexity);
+  Benchmark* Complexity(BigO complexity = benchmark::oAuto);
 
   // Support for running multiple copies of the same benchmark concurrently
   // in multiple threads.  This may be useful when measuring the scaling

test/complexity_test.cc

@@ -40,7 +40,7 @@ static void BM_Complexity_O_N(benchmark::State& state) {
   state.SetComplexityN(state.range_x());
 }
 BENCHMARK(BM_Complexity_O_N) -> RangeMultiplier(2) -> Range(1<<10, 1<<16) -> Complexity(benchmark::oN);
-BENCHMARK(BM_Complexity_O_N) -> RangeMultiplier(2) -> Range(1<<10, 1<<16) -> Complexity(benchmark::oAuto);
+BENCHMARK(BM_Complexity_O_N) -> RangeMultiplier(2) -> Range(1<<10, 1<<16) -> Complexity();
 
 static void BM_Complexity_O_N_Squared(benchmark::State& state) {
   std::string s1(state.range_x(), '-');