Use VTTScanner for VTT region settings parsing

Source/core/html/track/vtt/VTTParser.cpp

Index: Source/core/html/track/vtt/VTTParser.cpp
diff --git a/Source/core/html/track/vtt/VTTParser.cpp b/Source/core/html/track/vtt/VTTParser.cpp
index d5e30a3a6528b6e1db5e82c6ce133bd26d41f1aa..6dca478c09fe562de4e418a7e7ed76c019ab5cdf 100644
--- a/Source/core/html/track/vtt/VTTParser.cpp
+++ b/Source/core/html/track/vtt/VTTParser.cpp
@@ -60,14 +60,6 @@ unsigned VTTParser::collectDigitsToInt(const String& input, unsigned* position,
     return inputScanner.scanDigits(number);
 }
 
-String VTTParser::collectWord(const String& input, unsigned* position)
-{
-    StringBuilder string;
-    while (*position < input.length() && !isASpace(input[*position]))
-        string.append(input[(*position)++]);
-    return string.toString();
-}
-
 bool VTTParser::parseFloatPercentageValue(const String& value, float& percentage)
 {
     // '%' must be present and at the end of the setting value.