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

chrome/test/chromedriver/capabilities.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 "chrome/test/chromedriver/capabilities.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 377 matching lines @@
 }
 
 std::string Switches::ToString() const {
   std::string str;
   SwitchMap::const_iterator iter = switch_map_.begin();
   while (iter != switch_map_.end()) {
     str += "--" + iter->first;
     std::string value = GetSwitchValue(iter->first);
     if (value.length()) {
       if (value.find(' ') != std::string::npos)
-        value = base::GetDoubleQuotedJson(value);
+        value = base::GetQuotedJSONString(value);
       str += "=" + value;
     }
     ++iter;
     if (iter == switch_map_.end())
       break;
     str += " ";
   }
   return str;
 }
 
@@ skipping 23 matching lines @@
     if (desired_caps.Get(it->first, &capability)) {
       Status status = it->second.Run(*capability, this);
       if (status.IsError()) {
         return Status(
             kUnknownError, "cannot parse capability: " + it->first, status);
       }
     }
   }
   return Status(kOk);
 }