Revert "Simplify TurboFan's c1visualizer file handling."

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 152c936b98cef04789b17e826b97d439ef672315..6caaf19c8a4ffed90ff61db56faf0fe5bb1ec563 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1951,8 +1951,12 @@ bool Isolate::Init(Deserializer* des) {
   if (!create_heap_objects) Assembler::QuietNaN(heap_.nan_value());
 
   if (FLAG_trace_turbo) {
-    // Create an empty file.
-    std::ofstream(GetTurboCfgFileName(), std::ios_base::trunc);
+    // Erase the file.
+    char buffer[512];
+    Vector<char> filename(buffer, sizeof(buffer));
+    GetTurboCfgFileName(filename);
+    std::ofstream turbo_cfg_stream(filename.start(),
+                                   std::fstream::out | std::fstream::trunc);
   }
 
   // If we are deserializing, log non-function code objects and compiled
@@ -2368,11 +2372,13 @@ BasicBlockProfiler* Isolate::GetOrCreateBasicBlockProfiler() {
 }
 
 
-std::string Isolate::GetTurboCfgFileName() {
-  return FLAG_trace_turbo_cfg_file == NULL
-             ? "turbo-" + std::to_string(base::OS::GetCurrentProcessId()) +
-                   "-" + std::to_string(id()) + ".cfg"
-             : FLAG_trace_turbo_cfg_file;
+void Isolate::GetTurboCfgFileName(Vector<char> filename) {
+  if (FLAG_trace_turbo_cfg_file == NULL) {
+    SNPrintF(filename, "turbo-%d-%d.cfg", base::OS::GetCurrentProcessId(),
+             id());
+  } else {
+    StrNCpy(filename, FLAG_trace_turbo_cfg_file, filename.length());
+  }
 }