Add [TreatReturnedNullStringAs] support for ByteString.

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 220 matching lines @@
     [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=NullString] attribute DOMString treatNullAsNullStringStringAttribute;
     [TreatReturnedNullStringAs=Null] attribute DOMString treatReturnedNullStringAsNullStringAttribute;
     [TreatReturnedNullStringAs=Undefined] attribute DOMString treatReturnedNullStringAsUndefinedStringAttribute;
+    [TreatReturnedNullStringAs=Null] attribute ByteString treatReturnedNullStringAsNullByteStringAttribute;
+    [TreatReturnedNullStringAs=Undefined] attribute ByteString treatReturnedNullStringAsUndefinedByteStringAttribute;
     [TypeChecking=Interface|Nullable] attribute float typeCheckingInterfaceNullableStringFloatAttribute; // nop for non-interface types
     [TypeChecking=Interface] attribute TestInterface typeCheckingInterfaceTestInterfaceAttribute;
     [TypeChecking=Nullable] attribute TestInterface? typeCheckingNullableTestInterfaceOrNullAttribute;
     [TypeChecking=Interface|Nullable] attribute TestInterface? typeCheckingInterfaceNullableTestInterfaceOrNullAttribute;
     [Reflect, URL] attribute DOMString urlStringAttribute;
     [Reflect=reflectUrlAttribute, URL] attribute DOMString urlStringAttribute;
     [Unforgeable] attribute long unforgeableLongAttribute;
     [LogActivity=SetterOnly, LogPreviousValue] attribute long activityLoggingSetterOnlyLogPreviousValueAttribute;
     [LogActivity, LogPreviousValue] attribute TestInterfaceEmpty activityLoggingLogPreviousValueInterfaceAttribute;
 
@@ skipping 239 matching lines @@
     [NotEnumerable, ReadOnly] void notEnumerableReadOnlyVoidMethod();
     [RuntimeEnabled=FeatureName] void runtimeEnabledVoidMethod();
     [PerWorldBindings, RuntimeEnabled=FeatureName] void perWorldBindingsRuntimeEnabledVoidMethod();
     [RuntimeEnabled=FeatureName] void runtimeEnabledOverloadedVoidMethod(DOMString stringArg);
     [RuntimeEnabled=FeatureName] void runtimeEnabledOverloadedVoidMethod(long longArg);
     [RuntimeEnabled=FeatureName1] void partiallyRuntimeEnabledOverloadedVoidMethod(DOMString stringArg);
     [RuntimeEnabled=FeatureName2] void partiallyRuntimeEnabledOverloadedVoidMethod(TestInterface testInterface);
     void partiallyRuntimeEnabledOverloadedVoidMethod(long longArg);
     [TreatReturnedNullStringAs=Null] DOMString treatReturnedNullStringAsNullStringMethod();
     [TreatReturnedNullStringAs=Undefined] DOMString treatReturnedNullStringAsUndefinedStringMethod();
+    [TreatReturnedNullStringAs=Null] ByteString treatReturnedNullStringAsNullByteStringMethod();
+    [TreatReturnedNullStringAs=Undefined] ByteString treatReturnedNullStringAsUndefinedByteStringMethod();
     [TypeChecking=Interface] void typeCheckingInterfaceVoidMethodTestInterfaceEmptyArg(TestInterfaceEmpty testInterfaceEmptyArg);
     [TypeChecking=Nullable] void typeCheckingNullableVoidMethodTestInterfaceEmptyOrNullArg(TestInterfaceEmpty? testInterfaceEmptyOrNullArg);
     [TypeChecking=Interface|Nullable] void typeCheckingInterfaceNullableVoidMethodTestInterfaceEmptyOrNullArg(TestInterfaceEmpty? testInterfaceEmptyOrNullArg);
     [TypeChecking=Unrestricted] void typeCheckingUnrestrictedVoidMethodFloatArgDoubleArg(float floatArg, double doubleArg);
     [Unforgeable] void unforgeableVoidMethod();
     void voidMethodTestInterfaceGarbageCollectedSequenceArg(sequence<TestInterfaceGarbageCollected> testInterfaceGarbageCollectedSequenceArg);
     void voidMethodTestInterfaceGarbageCollectedArrayArg(TestInterfaceGarbageCollected[] testInterfaceGarbageCollectedArrayArg);
     void voidMethodTestInterfaceWillBeGarbageCollectedSequenceArg(sequence<TestInterfaceWillBeGarbageCollected> testInterfaceWillBeGarbageCollectedSequenceArg);
     void voidMethodTestInterfaceWillBeGarbageCollectedArrayArg(TestInterfaceWillBeGarbageCollected[] testInterfaceWillBeGarbageCollectedArrayArg);
 
     // Extended attributes on referenced interfaces
     // (not self; self-reference tests at interface themselves)
     attribute TestInterface testInterfaceAttribute; // [ImplementedAs]
     attribute TestInterfaceGarbageCollected testInterfaceGarbageCollectedAttribute; // [GarbageCollected]
     attribute TestInterfaceGarbageCollected? testInterfaceGarbageCollectedOrNullAttribute; // [GarbageCollected]
     attribute TestInterfaceWillBeGarbageCollected testInterfaceWillBeGarbageCollectedAttribute; // [WillBeGarbageCollected]
     attribute TestInterfaceWillBeGarbageCollected? testInterfaceWillBeGarbageCollectedOrNullAttribute; // [WillBeGarbageCollected]
 };