Make TracedValue lower overhead.

base/json/json_writer.h

 // Copyright (c) 2012 The Chromium 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 BASE_JSON_JSON_WRITER_H_
 #define BASE_JSON_JSON_WRITER_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 30 matching lines @@
   // TODO(tc): Should we generate json if it would be invalid json (e.g.,
   // |node| is not a DictionaryValue/ListValue or if there are inf/-inf float
   // values)?
   static void Write(const Value* const node, std::string* json);
 
   // Same as above but with |options| which is a bunch of JSONWriter::Options
   // bitwise ORed together.
   static void WriteWithOptions(const Value* const node, int options,
                                std::string* json);
 
+  // Returns a JSON compliant string representation of a double value.
+  static std::string DoubleToFormattedString(double value,
+      bool omit_double_type_preservation);
+
   // A static, constant JSON string representing an empty array.  Useful
   // for empty JSON argument passing.
   static const char* kEmptyArray;
 
  private:
   JSONWriter(bool escape, bool omit_binary_values,
              bool omit_double_type_preservation, bool pretty_print,
              std::string* json);
 
   // Called recursively to build the JSON string.  Whe completed, value is
@@ skipping 13 matching lines @@
 
   // Where we write JSON data as we generate it.
   std::string* json_string_;
 
   DISALLOW_COPY_AND_ASSIGN(JSONWriter);
 };
 
 }  // namespace base
 
 #endif  // BASE_JSON_JSON_WRITER_H_