IDL: Add support for [TreatNullAs=EmptyString]

Source/bindings/tests/idls/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 222 matching lines @@
     [Reflect, ReflectOnly="anonymous"|"use-credentials", ReflectEmpty="anonymous", ReflectInvalid="anonymous"] readonly attribute DOMString corsSettingAttribute;
     [Reflect, ReflectOnly="empty"|"missing"|"invalid"|"a-normal", ReflectEmpty="empty", ReflectMissing="missing", ReflectInvalid="invalid"] readonly attribute DOMString limitedWithEmptyMissingInvalidAttribute;
 
     [Replaceable] readonly attribute long replaceableReadonlyLongAttribute;
     [Replaceable, PutForwards=href] readonly attribute TestNode locationReplaceable;
     [RuntimeEnabled=FeatureName] attribute long runtimeEnabledLongAttribute;
     [PerContextEnabled=FeatureName, RuntimeEnabled=FeatureName] attribute long perContextEnabledRuntimeEnabledLongAttribute;
     [Conditional=CONDITION, RuntimeEnabled=FeatureName] attribute long conditionalRuntimeEnabledLongAttribute;
     [SetterCallWith=ActiveWindow&FirstWindow] attribute DOMString setterCallWithActiveWindowAndFirstWindowStringAttribute;
     [SetterCallWith=ExecutionContext] attribute DOMString setterCallWithExecutionContextStringAttribute;
+    [TreatNullAs=EmptyString] attribute DOMString treatNullAsEmptyStringStringAttribute;
     [TreatNullAs=NullString] attribute DOMString treatNullAsNullStringStringAttribute;
     [TreatReturnedNullStringAs=Null] attribute DOMString treatReturnedNullStringAsNullStringAttribute;
     [TreatReturnedNullStringAs=Undefined] attribute DOMString treatReturnedNullStringAsUndefinedStringAttribute;
     [TreatReturnedNullStringAs=Undefined, CachedAttribute=isStringDirty] attribute DOMString cachedTreatReturnedNullStringAsUndefinedStringAttribute;
     [TreatReturnedNullStringAs=Null] attribute ByteString treatReturnedNullStringAsNullByteStringAttribute;
     [TreatReturnedNullStringAs=Undefined] attribute ByteString treatReturnedNullStringAsUndefinedByteStringAttribute;
     [TreatReturnedNullStringAs=Null] attribute ScalarValueString treatReturnedNullStringAsNullScalarValueStringAttribute;
     [TreatReturnedNullStringAs=Undefined] attribute ScalarValueString treatReturnedNullStringAsUndefinedScalarValueStringAttribute;
     [TypeChecking=Interface] attribute float typeCheckingInterfaceFloatAttribute; // nop for non-interface types
     [TypeChecking=Interface] attribute TestInterface typeCheckingInterfaceTestInterfaceAttribute;
@@ skipping 188 matching lines @@
     // [Clamp]
     void voidMethodClampUnsignedShortArg([Clamp] unsigned short clampUnsignedShortArg);
     void voidMethodClampUnsignedLongArg([Clamp] unsigned long clampUnsignedLongArg);
     // [Default]
     void voidMethodDefaultUndefinedTestInterfaceEmptyArg([Default=Undefined] optional TestInterfaceEmpty defaultUndefinedTestInterfaceEmptyArg);
     void voidMethodDefaultUndefinedLongArg([Default=Undefined] optional long defaultUndefinedLongArg);
     void voidMethodDefaultUndefinedStringArg([Default=Undefined] optional DOMString defaultUndefinedStringArg);
     // [EnforceRange]
     void voidMethodEnforceRangeLongArg([EnforceRange] long enforceRangeLongArg);
     // [TreatNullAs], [TreatUndefinedAs]
+    void voidMethodTreatNullAsEmptyStringStringArg([TreatNullAs=EmptyString] DOMString treatNullAsEmptyStringStringArg);
     void voidMethodTreatNullAsNullStringStringArg([TreatNullAs=NullString] DOMString treatNullAsNullStringStringArg);
     void voidMethodTreatNullAsNullStringTreatUndefinedAsNullStringStringArg([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString treatNullAsNullStringStringArg);
 
     // Extended attributes for methods
     [LogActivity, LogAllWorlds] void activityLoggingAccessForAllWorldsMethod();
     [CallWith=ExecutionContext] void callWithExecutionContextVoidMethod();
     [CallWith=ScriptState] void callWithScriptStateVoidMethod();
     [CallWith=ScriptState] long callWithScriptStateLongMethod();
     [CallWith=ScriptState&ExecutionContext] void callWithScriptStateExecutionContextVoidMethod();
     [CallWith=ScriptState&ScriptArguments] void callWithScriptStateScriptArgumentsVoidMethod();
@@ skipping 74 matching lines @@
     [ImplementedInPrivateScript] short shortMethodWithShortArgumentImplementedInPrivateScript(short value);
     [ImplementedInPrivateScript] DOMString stringMethodWithStringArgumentImplementedInPrivateScript(DOMString value);
     [ImplementedInPrivateScript] Node nodeMethodWithNodeArgumentImplementedInPrivateScript(Node value);
     [ImplementedInPrivateScript] Node nodeMethodWithVariousArgumentsImplementedInPrivateScript(Document document, Node node, short value1, double value2, DOMString string);
     [ImplementedInPrivateScript] readonly attribute short readonlyShortAttribute;
     [ImplementedInPrivateScript] attribute short shortAttribute;
     [ImplementedInPrivateScript] attribute DOMString stringAttribute;
     [ImplementedInPrivateScript] attribute Node nodeAttribute;
 
 };