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

Source/core/css/MediaQuery.cpp

Index: Source/core/css/MediaQuery.cpp
diff --git a/Source/core/css/MediaQuery.cpp b/Source/core/css/MediaQuery.cpp
index bf819d1b3fe97eb549edab231c29e0829eb20044..14160589d4ae675382ec5d7803e01a18f394a148 100644
--- a/Source/core/css/MediaQuery.cpp
+++ b/Source/core/css/MediaQuery.cpp
@@ -43,10 +43,10 @@ String MediaQuery::serialize() const
     StringBuilder result;
     switch (m_restrictor) {
     case MediaQuery::Only:
-        result.append("only ");
+        result.appendLiteral("only ");
         break;
     case MediaQuery::Not:
-        result.append("not ");
+        result.appendLiteral("not ");
         break;
     case MediaQuery::None:
         break;
@@ -59,12 +59,12 @@ String MediaQuery::serialize() const
 
     if (m_mediaType != MediaTypeNames::all || m_restrictor != None) {
         result.append(m_mediaType);
-        result.append(" and ");
+        result.appendLiteral(" and ");
     }
 
     result.append(m_expressions->at(0)->serialize());
     for (size_t i = 1; i < m_expressions->size(); ++i) {
-        result.append(" and ");
+        result.appendLiteral(" and ");
         result.append(m_expressions->at(i)->serialize());
     }
     return result.toString();