Simplify TurboFan's c1visualizer file handling.

src/isolate.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include "include/v8-debug.h"
 #include "src/allocation.h"
 #include "src/assert-scope.h"
@@ skipping 1095 matching lines @@
   void RunMicrotasks();
 
   void SetUseCounterCallback(v8::Isolate::UseCounterCallback callback);
   void CountUsage(v8::Isolate::UseCounterFeature feature);
 
   BasicBlockProfiler* GetOrCreateBasicBlockProfiler();
   BasicBlockProfiler* basic_block_profiler() { return basic_block_profiler_; }
 
   static Isolate* NewForTesting() { return new Isolate(false); }
 
-  void GetTurboCfgFileName(Vector<char> buffer);
+  std::string GetTurboCfgFileName();
 
  private:
   explicit Isolate(bool enable_serializer);
 
   friend struct GlobalState;
   friend struct InitializeGlobalState;
 
   // These fields are accessed through the API, offsets must be kept in sync
   // with v8::internal::Internals (in include/v8.h) constants. This is also
   // verified in Isolate::Init() using runtime checks.
@@ skipping 424 matching lines @@
   }
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ISOLATE_H_