Use StringBuilder::appendLiteral() / StringBuilder::append(char) when possible

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

 /*
  * Copyright (C) 2011 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 273 matching lines @@
     }
     // Step 35.
     if (line.contains("-->")) {
         // Step 39-40.
         createNewCue();
 
         // Step 41 - New iteration of the cue loop.
         return recoverCue(line);
     }
     if (!m_currentContent.isEmpty())
-        m_currentContent.append("\n");
+        m_currentContent.append('\n');
     m_currentContent.append(line);
 
     return CueText;
 }
 
 VTTParser::ParseState VTTParser::recoverCue(const String& line)
 {
     // Step 17 and 21.
     resetCueValues();
 
@@ skipping 255 matching lines @@
 }
 
 void VTTParser::trace(Visitor* visitor)
 {
     visitor->trace(m_document);
     visitor->trace(m_cueList);
     visitor->trace(m_regionList);
 }
 
 }