[Tracing] Create TraceConfig JSON string parser in D8.

src/libplatform/tracing/trace-config.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 <string.h>
 
 #include "include/libplatform/v8-tracing.h"
 #include "src/base/logging.h"
 
 namespace v8 {
 
 class Isolate;
 
 namespace platform {
 namespace tracing {
 
+TraceConfig* TraceConfig::CreateDefaultTraceConfig() {
+  TraceConfig* trace_config = new TraceConfig();
+  trace_config->included_categories_.push_back("v8");
+  return trace_config;
+}
+
 bool TraceConfig::IsCategoryGroupEnabled(const char* category_group) const {
   for (auto included_category : included_categories_) {
     if (strcmp(included_category.data(), category_group) == 0) return true;
   }
   return false;
 }
 
 void TraceConfig::AddIncludedCategory(const char* included_category) {
   DCHECK(included_category != NULL && strlen(included_category) > 0);
   included_categories_.push_back(included_category);
 }
 
 void TraceConfig::AddExcludedCategory(const char* excluded_category) {
   DCHECK(excluded_category != NULL && strlen(excluded_category) > 0);
   excluded_categories_.push_back(excluded_category);
 }
 
 }  // namespace tracing
 }  // namespace platform
 }  // namespace v8