[turbofan] Make Pipeline more private.

src/compiler/pipeline.cc

Index: src/compiler/pipeline.cc
diff --git a/src/compiler/pipeline.cc b/src/compiler/pipeline.cc
index 107deac38e1971cfb2d6c4fd5c37fa58ab68a4c0..5a48c776d8e6b020d57b16a217ba3d45cbebae13 100644
--- a/src/compiler/pipeline.cc
+++ b/src/compiler/pipeline.cc
@@ -505,6 +505,8 @@ PipelineStatistics* CreatePipelineStatistics(CompilationInfo* info,
   return pipeline_statistics;
 }
 
+}  // namespace
+
 class PipelineCompilationJob final : public CompilationJob {
  public:
   PipelineCompilationJob(Isolate* isolate, Handle<JSFunction> function)
@@ -587,8 +589,6 @@ PipelineCompilationJob::Status PipelineCompilationJob::GenerateCodeImpl() {
   return SUCCEEDED;
 }
 
-}  // namespace
-
 class PipelineWasmCompilationJob final : public CompilationJob {
  public:
   explicit PipelineWasmCompilationJob(CompilationInfo* info, Graph* graph,