Make incremental marking tracing format consistent with GC tracing.

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 <memory>
 #include <queue>
 
@@ skipping 1147 matching lines @@
   bool IsInAnyContext(Object* object, uint32_t index);
 
   void SetRAILMode(RAILMode rail_mode);
 
   void IsolateInForegroundNotification();
 
   void IsolateInBackgroundNotification();
 
   bool IsIsolateInBackground() { return is_isolate_in_background_; }
 
+  void PrintWithTimestamp(const char* format, ...);
+
  protected:
   explicit Isolate(bool enable_serializer);
   bool IsArrayOrObjectPrototype(Object* object);
 
  private:
   friend struct GlobalState;
   friend struct InitializeGlobalState;
   Handle<JSObject> SetUpSubregistry(Handle<JSObject> registry, Handle<Map> map,
                                     const char* name);
 
@@ skipping 496 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_