Fix StrictTypeChecking on interface type attributes

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 204 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;
     [StrictTypeChecking] attribute float strictTypeCheckingFloatAttribute; // nop for non-interface types
     [StrictTypeChecking] attribute TestInterface strictTypeCheckingTestInterfaceAttribute;
+    [StrictTypeChecking] attribute TestInterface? strictTypeCheckingNullableTestInterfaceAttribute;
     [TreatNullAs=NullString] attribute DOMString treatNullAsNullStringStringAttribute;
     [TreatReturnedNullStringAs=Null] attribute DOMString treatReturnedNullStringAsNullStringAttribute;
     [TreatReturnedNullStringAs=Undefined] attribute DOMString treatReturnedNullStringAsUndefinedStringAttribute;
     [Reflect, URL] attribute DOMString urlStringAttribute;
     [Reflect=reflectUrlAttribute, URL] attribute DOMString urlStringAttribute;
     [Unforgeable] attribute long unforgeableLongAttribute;
 
 
     // Methods
     //
@@ skipping 226 matching lines @@
     // [WillBeGarbageCollected]
     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 TestInterfaceWillBeGarbageCollected testInterfaceWillBeGarbageCollectedAttribute; // [WillBeGarbageCollected]
     attribute TestInterfaceWillBeGarbageCollected? testInterfaceWillBeGarbageCollectedOrNullAttribute; // [WillBeGarbageCollected]
 };