message: [Executor] Fix measurement error in the microbenchmark.
  Previously, we were measuring the time taken to build the input graph, which
  dominated the cost of actually executing the executor code to be benchmarked.
diff: @@ -416,6 +416,7 @@ TEST_F(ExecutorTest, RecvInvalidRefDtype) {
  // maximum of 'width' nodes. All nodes are no-ops and all dependencies are
  // control dependencies.
  static void BM_executor(int iters, int width, int depth) {
  + testing::StopTiming();
  #ifdef PLATFORM_GOOGLE
  BenchmarkUseRealTime();
  #endif // PLATFORM_GOOGLE
  @@ -451,6 +452,7 @@ static void BM_executor(int iters, int width, int depth) {
  SetBenchmarkLabel(strings::StrCat("Nodes = ", cur));
  SetBenchmarkItemsProcessed(cur * static_cast<int64>(iters));
  #endif // PLATFORM_GOOGLE
  + testing::StartTiming();
  test::Benchmark("cpu", g).Run(iters);
  }
  @@ -466,6 +468,7 @@ BENCHMARK(BM_executor)->ArgPair(8192, 32);
  BENCHMARK(BM_executor)->ArgPair(1024, 1024);
  static void BM_FeedInputFetchOutput(int iters) {
  + testing::StopTiming();
  Graph* g = new Graph(OpRegistry::Global());
  // z = x + y: x and y are provided as benchmark inputs. z is the
  // output of the benchmark. Conceptually, the caller is ALICE, the
  @@ -484,6 +487,7 @@ static void BM_FeedInputFetchOutput(int iters) {
  #ifdef PLATFORM_GOOGLE
  SetBenchmarkItemsProcessed(static_cast<int64>(iters));
  #endif // PLATFORM_GOOGLE
  + testing::StartTiming();
  test::Benchmark("cpu", g).RunWithRendezvousArgs({{x_key, val}, {y_key, val}},
  {z_key}, iters);
  }
  