[tubofan] Remove .dot output of --trace-turbo

src/compiler/graph-visualizer.h

Index: src/compiler/graph-visualizer.h
diff --git a/src/compiler/graph-visualizer.h b/src/compiler/graph-visualizer.h
index d719540e2316271eebe682a87ee00ec0ab156080..8dbf89df4541bfd6afb24a578938e9cfe56b6be9 100644
--- a/src/compiler/graph-visualizer.h
+++ b/src/compiler/graph-visualizer.h
@@ -24,14 +24,6 @@ class SourcePositionTable;
 FILE* OpenVisualizerLogFile(CompilationInfo* info, const char* phase,
                             const char* suffix, const char* mode);
 
-struct AsDOT {
-  explicit AsDOT(const Graph& g) : graph(g) {}
-  const Graph& graph;
-};
-
-std::ostream& operator<<(std::ostream& os, const AsDOT& ad);
-
-
 struct AsJSON {
   AsJSON(const Graph& g, SourcePositionTable* p) : graph(g), positions(p) {}
   const Graph& graph;
@@ -76,7 +68,6 @@ struct AsC1VRegisterAllocationData {
   const RegisterAllocationData* data_;
 };
 
-std::ostream& operator<<(std::ostream& os, const AsDOT& ad);
 std::ostream& operator<<(std::ostream& os, const AsC1VCompilation& ac);
 std::ostream& operator<<(std::ostream& os, const AsC1V& ac);
 std::ostream& operator<<(std::ostream& os,