[Tracing] V8 Tracing Controller - Add args and copy support

src/libplatform/tracing/trace-writer.h

Index: src/libplatform/tracing/trace-writer.h
diff --git a/src/libplatform/tracing/trace-writer.h b/src/libplatform/tracing/trace-writer.h
index d12ed4bffbc3277cfd89e65dca0110539b2a86c4..963fc6a64dc262172db2949cc4f4f568d4fae8b1 100644
--- a/src/libplatform/tracing/trace-writer.h
+++ b/src/libplatform/tracing/trace-writer.h
@@ -19,6 +19,8 @@ class JSONTraceWriter : public TraceWriter {
   void Flush() override;
 
  private:
+  void AppendArgValue(uint8_t type, TraceObject::ArgValue value);
+
   std::ostream& stream_;
   bool append_comma_ = false;
 };