[Tracing] Create TraceConfig JSON string parser in D8.

include/libplatform/v8-tracing.h

Index: include/libplatform/v8-tracing.h
diff --git a/include/libplatform/v8-tracing.h b/include/libplatform/v8-tracing.h
index 9f6208ee46b7e14cf7ea5059aed745e95cf20130..4b1eb3c3637b34917a214c341d452acd3c2d550c 100644
--- a/include/libplatform/v8-tracing.h
+++ b/include/libplatform/v8-tracing.h
@@ -166,6 +166,8 @@ class TraceConfig {
  public:
   typedef std::vector<std::string> StringList;
 
+  static TraceConfig* CreateDefaultTraceConfig();
+
   TraceConfig()
       : enable_sampling_(false),
         enable_systrace_(false),
@@ -174,6 +176,8 @@ class TraceConfig {
   bool IsSamplingEnabled() const { return enable_sampling_; }
   bool IsSystraceEnabled() const { return enable_systrace_; }
   bool IsArgumentFilterEnabled() const { return enable_argument_filter_; }
+  StringList& GetIncludedCategories() { return included_categories_; }
+  StringList& GetExcludedCategories() { return excluded_categories_; }
 
   void SetTraceRecordMode(TraceRecordMode mode) { record_mode_ = mode; }
   void EnableSampling() { enable_sampling_ = true; }