Revert of [tracing] Support ConvertableToTraceFormat argument type.

src/libplatform/default-platform.cc

Index: src/libplatform/default-platform.cc
diff --git a/src/libplatform/default-platform.cc b/src/libplatform/default-platform.cc
index b8319ea3a9352b06523f5fa75f69ab6bb93f0405..2f81248ec189cefddeeb3ba7d12b898fdecdc7c4 100644
--- a/src/libplatform/default-platform.cc
+++ b/src/libplatform/default-platform.cc
@@ -178,17 +178,16 @@
          static_cast<double>(base::Time::kMicrosecondsPerSecond);
 }
 
+
 uint64_t DefaultPlatform::AddTraceEvent(
     char phase, const uint8_t* category_enabled_flag, const char* name,
     const char* scope, uint64_t id, uint64_t bind_id, int 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) {
+    const uint64_t* arg_values, unsigned int flags) {
   if (tracing_controller_) {
     return tracing_controller_->AddTraceEvent(
         phase, category_enabled_flag, name, scope, id, bind_id, num_args,
-        arg_names, arg_types, arg_values, arg_convertables, flags);
+        arg_names, arg_types, arg_values, flags);
   }
 
   return 0;