actualize commentary

DoubleToStringConverter::CreateDecimalRepresentation branch for ``decimal_point <= 0`` may require appending result_builder with zeroes when called from ToFixed, add corresponding commentary.
diff --git a/double-conversion/double-conversion.cc b/double-conversion/double-conversion.cc
index d82150b..720cda1 100644
--- a/double-conversion/double-conversion.cc
+++ b/double-conversion/double-conversion.cc
@@ -118,7 +118,7 @@
     StringBuilder* result_builder) const {
   // Create a representation that is padded with zeros if needed.
   if (decimal_point <= 0) {
-      // "0.00000decimal_rep".
+      // "0.00000decimal_rep" or "0.000decimal_rep00"
     result_builder->AddCharacter('0');
     if (digits_after_point > 0) {
       result_builder->AddCharacter('.');