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

src/conversions.h

Index: src/conversions.h
diff --git a/src/conversions.h b/src/conversions.h
index c4ceea6b9086f38501dc445481e74bcf092247e4..9e32a0cdb536126897a23a20824a6f9fdde07597 100644
--- a/src/conversions.h
+++ b/src/conversions.h
@@ -96,8 +96,12 @@ static inline uint32_t NumberToUint32(Object* number);
 
 
 // Converts a string into a double value according to ECMA-262 9.3.1
-double StringToDouble(const char* str, int flags, double empty_string_val = 0);
 double StringToDouble(String* str, int flags, double empty_string_val = 0);
+double StringToDouble(Vector<const char> str,
+                      int flags,
+                      double empty_string_val = 0);
+// This version expects a zero-terminated character array.
+double StringToDouble(const char* str, int flags, double empty_string_val = 0);
 
 // Converts a string into an integer.
 double StringToInt(String* str, int radix);