Rewrite std::string("") to std::string(), Linux edition.

content/renderer/date_time_formatter.cc

Index: content/renderer/date_time_formatter.cc
diff --git a/content/renderer/date_time_formatter.cc b/content/renderer/date_time_formatter.cc
index d3c16e355c88b967e21f4ec50fa86fe60aa88631..1adb0debddf9fa2f5c44f7af58be0f8e25aa9665 100644
--- a/content/renderer/date_time_formatter.cc
+++ b/content/renderer/date_time_formatter.cc
@@ -95,7 +95,7 @@ const std::string DateTimeFormatter::FormatString() const {
   UErrorCode success = U_ZERO_ERROR;
   if (year_ == 0 && month_ == 0 && day_ == 0 &&
       hour_ == 0 && minute_ == 0 && second_ == 0) {
-    return "";
+    return std::string();
   }
 
   std::string result;
@@ -113,7 +113,7 @@ const std::string DateTimeFormatter::FormatString() const {
       return result;
   }
   LOG(WARNING) << "Calendar not created: error " <<  success;
-  return "";
+  return std::string();
 }
 
 void DateTimeFormatter::ExtractType(