Use the single char overload of append() when possible.

third_party/WebKit/Source/core/testing/DictionaryTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "DictionaryTest.h"
 
 #include "bindings/core/v8/V8ObjectBuilder.h"
 #include "core/testing/InternalDictionary.h"
 #include "core/testing/InternalDictionaryDerived.h"
 
@@ skipping 145 matching lines @@
         return emptyString();
 
     bool firstLoop = true;
     while (iterator.next(executionContext, exceptionState)) {
         if (exceptionState.hadException())
             return emptyString();
 
         if (firstLoop)
             firstLoop = false;
         else
-            result.append(",");
+            result.append(',');
 
         v8::Local<v8::Value> value;
         if (v8Call(iterator.value(), value))
             result.append(toCoreString(value->ToString()));
     }
 
     return result.toString();
 }
 
 void DictionaryTest::reset()
@@ skipping 30 matching lines @@
 
 DEFINE_TRACE(DictionaryTest)
 {
     visitor->trace(m_elementMember);
     visitor->trace(m_elementOrNullMember);
     visitor->trace(m_doubleOrStringSequenceMember);
     visitor->trace(m_eventTargetOrNullMember);
 }
 
 } // namespace blink