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

Source/platform/animation/TimingFunction.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 "config.h"
 #include "platform/animation/TimingFunction.h"
 
 #include "wtf/MathExtras.h"
 
 namespace blink {
@@ skipping 107 matching lines @@
     case StepsTimingFunction::Start:
         return "step-start";
     case StepsTimingFunction::Middle:
         return "step-middle";
     case StepsTimingFunction::End:
         return "step-end";
     case StepsTimingFunction::Custom:
         builder.append("steps(" + String::numberToStringECMAScript(this->numberOfSteps()) + ", ");
 
         if (this->stepAtPosition() == StepsTimingFunction::StepAtStart)
-            builder.append("start");
+            builder.appendLiteral("start");
         else if (this->stepAtPosition() == StepsTimingFunction::StepAtMiddle)
-            builder.append("middle");
+            builder.appendLiteral("middle");
         else if (this->stepAtPosition() == StepsTimingFunction::StepAtEnd)
-            builder.append("end");
+            builder.appendLiteral("end");
         else
             ASSERT_NOT_REACHED();
 
-        builder.append(")");
+        builder.append(')');
         break;
     default:
         ASSERT_NOT_REACHED();
     }
     return builder.toString();
 }
 
 void StepsTimingFunction::range(double* minValue, double* maxValue) const
 {
     *minValue = 0;
@@ skipping 73 matching lines @@
     return false;
 }
 
 // No need to define specific operator!= as they can all come via this function.
 bool operator!=(const TimingFunction& lhs, const TimingFunction& rhs)
 {
     return !(lhs == rhs);
 }
 
 } // namespace blink