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

Source/core/rendering/GraphicsContextAnnotator.cpp

Index: Source/core/rendering/GraphicsContextAnnotator.cpp
diff --git a/Source/core/rendering/GraphicsContextAnnotator.cpp b/Source/core/rendering/GraphicsContextAnnotator.cpp
index 227234162895bff1273175abefeb4a0c32693051..8276977da98c0baee828fd7ead89555fcfdc808e 100644
--- a/Source/core/rendering/GraphicsContextAnnotator.cpp
+++ b/Source/core/rendering/GraphicsContextAnnotator.cpp
@@ -112,7 +112,7 @@ void GraphicsContextAnnotator::annotate(const PaintInfo& paintInfo, const Render
             StringBuilder classBuilder;
             for (size_t i = 0; i < classes.size(); ++i) {
                 if (i > 0)
-                    classBuilder.append(" ");
+                    classBuilder.append(' ');
                 classBuilder.append(classes[i]);
             }