Created collector class and used it to collect identifiers during scanning.

src/conversions.cc

Index: src/conversions.cc
diff --git a/src/conversions.cc b/src/conversions.cc
index 1e2bb20c4f896882b2145489ad3736a91513ee02..90cdc773eabba36ecd47b113854d908ac1c4f8a3 100644
--- a/src/conversions.cc
+++ b/src/conversions.cc
@@ -733,11 +733,18 @@ double StringToInt(String* str, int radix) {
 
 double StringToDouble(const char* str, int flags, double empty_string_val) {
   const char* end = str + StrLength(str);
-
   return InternalStringToDouble(str, end, flags, empty_string_val);
 }
 
 
+double StringToDouble(Vector<const char> str,
+                      int flags,
+                      double empty_string_val) {
+  const char* end = str.start() + str.length();
+  return InternalStringToDouble(str.start(), end, flags, empty_string_val);
+}
+
+
 extern "C" char* dtoa(double d, int mode, int ndigits,
                       int* decpt, int* sign, char** rve);