[tracing] do not add traces when disabled

https://github.com/nodejs/node/issues/21038

Change-Id: Ic4c9f403b5e54a97d3170b2311dd5aab8c8357c8
Reviewed-on: https://chromium-review.googlesource.com/1217726
Commit-Queue: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55809}

src/libplatform/tracing/tracing-controller.cc

@@ -78,7 +78,8 @@ uint64_t TracingController::AddTraceEvent(
     const uint64_t* arg_values,
     std::unique_ptr<v8::ConvertableToTraceFormat>* arg_convertables,
     unsigned int flags) {
-  uint64_t handle;
+  uint64_t handle = 0;
+  if (mode_ != DISABLED) {
     TraceObject* trace_object = trace_buffer_->AddTraceEvent(&handle);
     if (trace_object) {
       trace_object->Initialize(
@@ -86,6 +87,7 @@ uint64_t TracingController::AddTraceEvent(
           arg_names, arg_types, arg_values, arg_convertables, flags,
           CurrentTimestampMicroseconds(), CurrentCpuTimestampMicroseconds());
     }
+  }
   return handle;
 }
 
@@ -96,7 +98,8 @@ uint64_t TracingController::AddTraceEventWithTimestamp(
     const uint64_t* arg_values,
     std::unique_ptr<v8::ConvertableToTraceFormat>* arg_convertables,
     unsigned int flags, int64_t timestamp) {
-  uint64_t handle;
+  uint64_t handle = 0;
+  if (mode_ != DISABLED) {
     TraceObject* trace_object = trace_buffer_->AddTraceEvent(&handle);
     if (trace_object) {
       trace_object->Initialize(phase, category_enabled_flag, name, scope, id,
@@ -104,6 +107,7 @@ uint64_t TracingController::AddTraceEventWithTimestamp(
                                arg_values, arg_convertables, flags, timestamp,
                                CurrentCpuTimestampMicroseconds());
     }
+  }
   return handle;
 }