[tracing] Support ConvertableToTraceFormat argument type.

src/libplatform/tracing/trace-writer.cc

 // Copyright 2016 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.
 
 #include "src/libplatform/tracing/trace-writer.h"
 
 #include <cmath>
 
 #include "base/trace_event/common/trace_event_common.h"
+#include "include/v8-platform.h"
 #include "src/base/platform/platform.h"
 
 namespace v8 {
 namespace platform {
 namespace tracing {
 
 // Writes the given string to a stream, taking care to escape characters
 // when necessary.
 V8_INLINE static void WriteJSONStringToStream(const char* str,
                                               std::ostream& stream) {
@@ skipping 85 matching lines @@
       } else {
         WriteJSONStringToStream(value.as_string, stream_);
       }
       break;
     default:
       UNREACHABLE();
       break;
   }
 }
 
+void JSONTraceWriter::AppendArgValue(ConvertableToTraceFormat* value) {
+  std::string arg_stringified;
+  value->AppendAsTraceFormat(&arg_stringified);
+  stream_ << arg_stringified;
+}
+
 JSONTraceWriter::JSONTraceWriter(std::ostream& stream) : stream_(stream) {
   stream_ << "{\"traceEvents\":[";
 }
 
 JSONTraceWriter::~JSONTraceWriter() { stream_ << "]}"; }
 
 void JSONTraceWriter::AppendTraceEvent(TraceObject* trace_event) {
   if (append_comma_) stream_ << ",";
   append_comma_ = true;
   stream_ << "{\"pid\":" << trace_event->pid()
@@ skipping 11 matching lines @@
       stream_ << ",\"scope\":\"" << trace_event->scope() << "\"";
     }
     // So as not to lose bits from a 64-bit integer, output as a hex string.
     stream_ << ",\"id\":\"0x" << std::hex << trace_event->id() << "\""
             << std::dec;
   }
   stream_ << ",\"args\":{";
   const char** arg_names = trace_event->arg_names();
   const uint8_t* arg_types = trace_event->arg_types();
   TraceObject::ArgValue* arg_values = trace_event->arg_values();
+  std::unique_ptr<v8::ConvertableToTraceFormat>* arg_convertables =
+      trace_event->arg_convertables();
   for (int i = 0; i < trace_event->num_args(); ++i) {
     if (i > 0) stream_ << ",";
     stream_ << "\"" << arg_names[i] << "\":";
-    AppendArgValue(arg_types[i], arg_values[i]);
+    if (arg_types[i] == TRACE_VALUE_TYPE_CONVERTABLE) {
+      AppendArgValue(arg_convertables[i].get());
+    } else {
+      AppendArgValue(arg_types[i], arg_values[i]);
+    }
   }
   stream_ << "}}";
   // TODO(fmeawad): Add support for Flow Events.
 }
 
 void JSONTraceWriter::Flush() {}
 
 TraceWriter* TraceWriter::CreateJSONTraceWriter(std::ostream& stream) {
   return new JSONTraceWriter(stream);
 }
 
 }  // namespace tracing
 }  // namespace platform
 }  // namespace v8