Stop doing unnecessary UTF-8 to UTF-16 conversions in JSONWriter.

tools/gn/trace.cc

 // Copyright (c) 2013 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.
 
 #include "tools/gn/trace.h"
 
 #include <algorithm>
 #include <map>
 #include <sstream>
 #include <vector>
@@ skipping 223 matching lines @@
     const TraceItem& item = *events[i];
 
     if (i != 0)
       out << ",";
     out << "{\"pid\":0,\"tid\":" << item.thread_id();
     out << ",\"ts\":" << item.begin().ToInternalValue();
     out << ",\"ph\":\"X\"";  // "X" = complete event with begin & duration.
     out << ",\"dur\":" << item.delta().InMicroseconds();
 
     quote_buffer.resize(0);
-    base::JsonDoubleQuote(item.name(), true, &quote_buffer);
+    base::EscapeJSONString(item.name(), true, &quote_buffer);
     out << ",\"name\":" << quote_buffer;
 
     out << ",\"cat\":";
     switch (item.type()) {
       case TraceItem::TRACE_FILE_LOAD:
         out << "\"load\"";
         break;
       case TraceItem::TRACE_FILE_PARSE:
         out << "\"parse\"";
         break;
       case TraceItem::TRACE_FILE_EXECUTE:
         out << "\"file_exec\"";
         break;
       case TraceItem::TRACE_FILE_WRITE:
         out << "\"file_write\"";
         break;
       case TraceItem::TRACE_SCRIPT_EXECUTE:
         out << "\"script_exec\"";
         break;
       case TraceItem::TRACE_DEFINE_TARGET:
         out << "\"define\"";
     }
 
     if (!item.toolchain().empty() || !item.cmdline().empty()) {
       out << ",\"args\":{";
       bool needs_comma = false;
       if (!item.toolchain().empty()) {
         quote_buffer.resize(0);
-        base::JsonDoubleQuote(item.toolchain(), true, &quote_buffer);
+        base::EscapeJSONString(item.toolchain(), true, &quote_buffer);
         out << "\"toolchain\":" << quote_buffer;
         needs_comma = true;
       }
       if (!item.cmdline().empty()) {
         quote_buffer.resize(0);
-        base::JsonDoubleQuote(item.cmdline(), true, &quote_buffer);
+        base::EscapeJSONString(item.cmdline(), true, &quote_buffer);
         if (needs_comma)
           out << ",";
         out << "\"cmdline\":" << quote_buffer;
         needs_comma = true;
       }
       out << "}";
     }
     out << "}";
   }
 
   out << "]}";
 
   std::string out_str = out.str();
   file_util::WriteFile(file_name, out_str.data(),
                        static_cast<int>(out_str.size()));
 }