Revert of [tracing] Support ConvertableToTraceFormat argument type.

src/libplatform/default-platform.h

Index: src/libplatform/default-platform.h
diff --git a/src/libplatform/default-platform.h b/src/libplatform/default-platform.h
index 3881fd2d022ca21e80dde9fc099822d01ca831a3..0fd7e5ad890a3090ab794c9d5c734a6ea29f45f3 100644
--- a/src/libplatform/default-platform.h
+++ b/src/libplatform/default-platform.h
@@ -51,13 +51,12 @@
   const uint8_t* GetCategoryGroupEnabled(const char* name) override;
   const char* GetCategoryGroupName(
       const uint8_t* category_enabled_flag) override;
-  uint64_t AddTraceEvent(
-      char phase, const uint8_t* category_enabled_flag, const char* name,
-      const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
-      const char** arg_names, const uint8_t* arg_types,
-      const uint64_t* arg_values,
-      std::unique_ptr<v8::ConvertableToTraceFormat>* arg_convertables,
-      unsigned int flags) override;
+  uint64_t AddTraceEvent(char phase, const uint8_t* category_enabled_flag,
+                         const char* name, const char* scope, uint64_t id,
+                         uint64_t bind_id, int32_t num_args,
+                         const char** arg_names, const uint8_t* arg_types,
+                         const uint64_t* arg_values,
+                         unsigned int flags) override;
   void UpdateTraceEventDuration(const uint8_t* category_enabled_flag,
                                 const char* name, uint64_t handle) override;
   void SetTracingController(tracing::TracingController* tracing_controller);