Revert of Revert of [turbofan] Small fixes to PipelineStatistics. Collect statistics in tests.

src/compiler/pipeline.cc

Index: src/compiler/pipeline.cc
diff --git a/src/compiler/pipeline.cc b/src/compiler/pipeline.cc
index fd8843fea69be49530c1d4caed02634fae40acf0..5e51c454cda8b73d296b443015f17a472b88c2e2 100644
--- a/src/compiler/pipeline.cc
+++ b/src/compiler/pipeline.cc
@@ -1139,6 +1139,12 @@
   // Construct a pipeline for scheduling and code generation.
   ZonePool zone_pool;
   PipelineData data(&zone_pool, info, graph, schedule);
+  SmartPointer<PipelineStatistics> pipeline_statistics;
+  if (FLAG_turbo_stats) {
+    pipeline_statistics.Reset(new PipelineStatistics(info, &zone_pool));
+    pipeline_statistics->BeginPhaseKind("test codegen");
+  }
+
   Pipeline pipeline(info);
   pipeline.data_ = &data;
   if (data.schedule() == nullptr) {