Rework float value/percentage scanning for VTTRegion

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

 /*
  * Copyright (C) 2013 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 230 matching lines @@
 {
     DEFINE_STATIC_LOCAL(const AtomicString, scrollUpValueKeyword, ("up", AtomicString::ConstructFromLiteral));
 
     switch (setting) {
     case Id:
         if (value.find("-->") == kNotFound)
             m_id = value;
         break;
     case Width: {
         float floatWidth;
-        if (VTTParser::parseFloatPercentageValue(value, floatWidth))
+        VTTScanner valueScanner(value);
+        if (VTTParser::parseFloatPercentageValue(valueScanner, floatWidth) && valueScanner.isAtEnd())
             m_width = floatWidth;
         else
             WTF_LOG(Media, "VTTRegion::parseSettingValue, invalid Width");
         break;
     }
     case Height: {
         unsigned position = 0;
         int number;
         if (VTTParser::collectDigitsToInt(value, &position, number) && position == value.length())
             m_heightInLines = number;
@@ skipping 187 matching lines @@
 
 void VTTRegion::scrollTimerFired(Timer<VTTRegion>*)
 {
     WTF_LOG(Media, "VTTRegion::scrollTimerFired");
 
     stopTimer();
     displayLastVTTCueBox();
 }
 
 } // namespace WebCore