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

third_party/WebKit/Source/web/tests/FrameTestHelpers.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 95 matching lines @@
 }
 
 // |uniqueName| is normally calculated in a somewhat complicated way by the
 // FrameTree class, but for test purposes the approximation below should be
 // close enough.
 String nameToUniqueName(const String& name)
 {
     static int uniqueNameCounter = 0;
     StringBuilder uniqueName;
     uniqueName.append(name);
-    uniqueName.append(" ");
+    uniqueName.append(' ');
     uniqueName.appendNumber(uniqueNameCounter++);
     return uniqueName.toString();
 }
 
 } // namespace
 
 void loadFrame(WebFrame* frame, const std::string& url)
 {
     WebURLRequest urlRequest;
     urlRequest.initialize();
@@ skipping 211 matching lines @@
     m_testWebViewClient->scheduleAnimation();
 }
 
 void TestWebViewWidgetClient::didMeaningfulLayout(WebMeaningfulLayout layoutType)
 {
     m_testWebViewClient->didMeaningfulLayout(layoutType);
 }
 
 } // namespace FrameTestHelpers
 } // namespace blink