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

Source/core/fileapi/FileReaderLoader.cpp

Index: Source/core/fileapi/FileReaderLoader.cpp
diff --git a/Source/core/fileapi/FileReaderLoader.cpp b/Source/core/fileapi/FileReaderLoader.cpp
index a713ec998dafd693f247cd53a8fa610591547522..055cff0ee574a8c453f67218fbf1a8fd97f17c35 100644
--- a/Source/core/fileapi/FileReaderLoader.cpp
+++ b/Source/core/fileapi/FileReaderLoader.cpp
@@ -382,7 +382,7 @@ void FileReaderLoader::convertToDataURL()
     m_isRawDataConverted = true;
 
     StringBuilder builder;
-    builder.append("data:");
+    builder.appendLiteral("data:");
 
     if (!m_bytesLoaded) {
         m_stringResult = builder.toString();
@@ -390,7 +390,7 @@ void FileReaderLoader::convertToDataURL()
     }
 
     builder.append(m_dataType);
-    builder.append(";base64,");
+    builder.appendLiteral(";base64,");
 
     Vector<char> out;
     base64Encode(static_cast<const char*>(m_rawData->data()), m_rawData->byteLength(), out);