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

Source/modules/websockets/DOMWebSocket.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 170 matching lines @@
     return true;
 }
 
 static String encodeSubprotocolString(const String& protocol)
 {
     StringBuilder builder;
     for (size_t i = 0; i < protocol.length(); i++) {
         if (protocol[i] < 0x20 || protocol[i] > 0x7E)
             builder.append(String::format("\\u%04X", protocol[i]));
         else if (protocol[i] == 0x5c)
-            builder.append("\\\\");
+            builder.appendLiteral("\\\\");
         else
             builder.append(protocol[i]);
     }
     return builder.toString();
 }
 
 static String joinStrings(const Vector<String>& strings, const char* separator)
 {
     StringBuilder builder;
     for (size_t i = 0; i < strings.size(); ++i) {
@@ skipping 486 matching lines @@
 
 void DOMWebSocket::trace(Visitor* visitor)
 {
     visitor->trace(m_channel);
     visitor->trace(m_eventQueue);
     WebSocketChannelClient::trace(visitor);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace blink