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

Source/core/html/forms/FormController.cpp

Index: Source/core/html/forms/FormController.cpp
diff --git a/Source/core/html/forms/FormController.cpp b/Source/core/html/forms/FormController.cpp
index afcc35577619b7d8fdeabdd16431fbd18d06030f..046e0b231cddc92ae26ee7a6a2374729ace996e9 100644
--- a/Source/core/html/forms/FormController.cpp
+++ b/Source/core/html/forms/FormController.cpp
@@ -317,7 +317,7 @@ static inline void recordFormStructure(const HTMLFormElement& form, StringBuilde
     // 2 is enough to distinguish forms in webkit.org/b/91209#c0
     const size_t namedControlsToBeRecorded = 2;
     const FormAssociatedElement::List& controls = form.associatedElements();
-    builder.append(" [");
+    builder.appendLiteral(" [");
     for (size_t i = 0, namedControls = 0; i < controls.size() && namedControls < namedControlsToBeRecorded; ++i) {
         if (!controls[i]->isFormControlElementWithState())
             continue;
@@ -329,9 +329,9 @@ static inline void recordFormStructure(const HTMLFormElement& form, StringBuilde
             continue;
         namedControls++;
         builder.append(name);
-        builder.append(" ");
+        builder.append(' ');
     }
-    builder.append("]");
+    builder.append(']');
 }
 
 static inline String formSignature(const HTMLFormElement& form)