[Tracing] Create TraceConfig JSON string parser in D8.

include/libplatform/v8-tracing.h

 // 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.
 
 #ifndef V8_LIBPLATFORM_V8_TRACING_H_
 #define V8_LIBPLATFORM_V8_TRACING_H_
 
 #include <fstream>
 #include <memory>
 #include <vector>
@@ skipping 148 matching lines @@
   RECORD_AS_MUCH_AS_POSSIBLE,
 
   // Echo to console. Events are discarded.
   ECHO_TO_CONSOLE,
 };
 
 class TraceConfig {
  public:
   typedef std::vector<std::string> StringList;
 
+  static TraceConfig* CreateDefaultTraceConfig();
+
   TraceConfig()
       : enable_sampling_(false),
         enable_systrace_(false),
         enable_argument_filter_(false) {}
   TraceRecordMode GetTraceRecordMode() const { return record_mode_; }
   bool IsSamplingEnabled() const { return enable_sampling_; }
   bool IsSystraceEnabled() const { return enable_systrace_; }
   bool IsArgumentFilterEnabled() const { return enable_argument_filter_; }
 
   void SetTraceRecordMode(TraceRecordMode mode) { record_mode_ = mode; }
@@ skipping 63 matching lines @@
   // Disallow copy and assign
   TracingController(const TracingController&) = delete;
   void operator=(const TracingController&) = delete;
 };
 
 }  // namespace tracing
 }  // namespace platform
 }  // namespace v8
 
 #endif  // V8_LIBPLATFORM_V8_TRACING_H_