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

sync/internal_api/public/base/progress_marker_map.cc

Index: sync/internal_api/public/base/progress_marker_map.cc
diff --git a/sync/internal_api/public/base/progress_marker_map.cc b/sync/internal_api/public/base/progress_marker_map.cc
index b2810134ebf30859e01725efabdc18dafdda2292..ea1f177b7d3e9703599c7d39b96e7e645534fb15 100644
--- a/sync/internal_api/public/base/progress_marker_map.cc
+++ b/sync/internal_api/public/base/progress_marker_map.cc
@@ -16,9 +16,8 @@ scoped_ptr<base::DictionaryValue> ProgressMarkerMapToValue(
   for (ProgressMarkerMap::const_iterator it = marker_map.begin();
        it != marker_map.end(); ++it) {
     std::string printable_payload;
-    base::JsonDoubleQuote(it->second,
-                          false /* put_in_quotes */,
-                          &printable_payload);
+    base::EscapeJSONString(
+        it->second, false /* put_in_quotes */, &printable_payload);
     value->SetString(ModelTypeToString(it->first), printable_payload);
   }
   return value.Pass();