IDL: Add [Custom=CallEpilogue] to eliminate CG special cases

Source/bindings/tests/idls/core/TestObject.idl

 /*
  * Copyright (C) 2013 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 496 matching lines @@
     [CallWith=ScriptState] long callWithScriptStateLongMethod();
     [CallWith=(ScriptState,ExecutionContext)] void callWithScriptStateExecutionContextVoidMethod();
     [CallWith=(ScriptState,ScriptArguments)] void callWithScriptStateScriptArgumentsVoidMethod();
     [CallWith=(ScriptState,ScriptArguments)] void callWithScriptStateScriptArgumentsVoidMethodOptionalBooleanArg(optional boolean optionalBooleanArg);
     [CallWith=ActiveWindow] void callWithActiveWindow();
     [CallWith=(ActiveWindow,FirstWindow)] void callWithActiveWindowScriptWindow();
     [CheckSecurity=Node] void checkSecurityForNodeVoidMethod();
     [Conditional=CONDITION] void conditionalConditionVoidMethod();
     [Conditional=CONDITION] static void conditionalConditionStaticVoidMethod();
     [Custom] void customVoidMethod();
+    [Custom=CallEpilogue] void customCallEpilogueVoidMethod();
     [Conditional=CONDITION, Custom] void conditionalConditionCustomVoidMethod();
     [CustomElementCallbacks] void customElementCallbacksVoidMethod();
     [DeprecateAs=voidMethod] void deprecatedVoidMethod();
     [DoNotCheckSignature] void doNotCheckSignatureVoidMethod();
     [ImplementedAs=implementedAsMethodName] void implementedAsVoidMethod();
     [MeasureAs=TestFeature] void measureAsVoidMethod();
     [Measure] void measureMethod();
     [Measure] void measureOverloadedMethod();
     [Measure] void measureOverloadedMethod(long arg);
     [DeprecateAs=TestFeatureA] void DeprecateAsOverloadedMethod();
@@ skipping 70 matching lines @@
     [ImplementedInPrivateScript] attribute DOMString stringAttribute;
     [ImplementedInPrivateScript] attribute Node nodeAttribute;
     [OnlyExposedToPrivateScript] short methodImplementedInCPPForPrivateScriptOnly(short value1, short value2);
     [OnlyExposedToPrivateScript] attribute DOMString attributeImplementedInCPPForPrivateScriptOnly;
     [ImplementedInPrivateScript, OnlyExposedToPrivateScript] short methodForPrivateScriptOnly(short value1, short value2);
     [ImplementedInPrivateScript, OnlyExposedToPrivateScript] attribute DOMString attributeForPrivateScriptOnly;
     [ImplementedInPrivateScript] attribute TestEnum enumForPrivateScript;
 
     maplike<long, DOMStringOrDouble>;
 };