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

Source/modules/websockets/WebSocketExtensionDispatcher.cpp

Index: Source/modules/websockets/WebSocketExtensionDispatcher.cpp
diff --git a/Source/modules/websockets/WebSocketExtensionDispatcher.cpp b/Source/modules/websockets/WebSocketExtensionDispatcher.cpp
index 397bae1bb61d168207b9243bb3e690751390982b..36ff82fb9bc3b15fb494bc437d4990745c3c850c 100644
--- a/Source/modules/websockets/WebSocketExtensionDispatcher.cpp
+++ b/Source/modules/websockets/WebSocketExtensionDispatcher.cpp
@@ -67,7 +67,7 @@ const String WebSocketExtensionDispatcher::createHeaderValue() const
     StringBuilder builder;
     builder.append(m_processors[0]->handshakeString());
     for (size_t i = 1; i < numProcessors; ++i) {
-        builder.append(", ");
+        builder.appendLiteral(", ");
         builder.append(m_processors[i]->handshakeString());
     }
     return builder.toString();
@@ -76,14 +76,14 @@ const String WebSocketExtensionDispatcher::createHeaderValue() const
 void WebSocketExtensionDispatcher::appendAcceptedExtension(const String& extensionToken, HashMap<String, String>& extensionParameters)
 {
     if (!m_acceptedExtensionsBuilder.isEmpty())
-        m_acceptedExtensionsBuilder.append(", ");
+        m_acceptedExtensionsBuilder.appendLiteral(", ");
     m_acceptedExtensionsBuilder.append(extensionToken);
     // FIXME: Should use ListHashSet to keep the order of the parameters.
     for (HashMap<String, String>::const_iterator iterator = extensionParameters.begin(); iterator != extensionParameters.end(); ++iterator) {
-        m_acceptedExtensionsBuilder.append("; ");
+        m_acceptedExtensionsBuilder.appendLiteral("; ");
         m_acceptedExtensionsBuilder.append(iterator->key);
         if (!iterator->value.isNull()) {
-            m_acceptedExtensionsBuilder.append("=");
+            m_acceptedExtensionsBuilder.append('=');
             m_acceptedExtensionsBuilder.append(iterator->value);
         }
     }