Explicitly mark first 2 args of addEventListener/removeEventListener as optional

Source/core/core.gypi

 {
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/Animation.idl',
             'animation/AnimationPlayer.idl',
             'animation/TimedItem.idl',
             'animation/Timeline.idl',
             'animation/Timing.idl',
             'clipboard/DataTransfer.idl',
@@ skipping 429 matching lines @@
             'xml/XMLHttpRequestProgressEvent.idl',
             'xml/XMLHttpRequestUpload.idl',
             'xml/XMLSerializer.idl',
             'xml/XPathEvaluator.idl',
             'xml/XPathExpression.idl',
             'xml/XPathNSResolver.idl',
             'xml/XPathResult.idl',
             'xml/XSLTProcessor.idl',
         ],
         # 'partial interface', target (right side of) 'implements', and
-        # static bindings (in bindings/v8/)
+        # interfaces with static bindings (in bindings/v8/)
         'core_dependency_idl_files': [
             'animation/DocumentAnimation.idl',
             'animation/ElementAnimation.idl',
             'css/DocumentFontFaceSet.idl',
             'dom/ChildNode.idl',
             'dom/DocumentFullscreen.idl',
             'dom/GlobalEventHandlers.idl',
             'dom/ParentNode.idl',
             'dom/URLUtils.idl',
             'dom/URLUtilsReadOnly.idl',
@@ skipping 2864 matching lines @@
             'html/track/vtt/BufferedLineReaderTest.cpp',
             'html/track/vtt/VTTScannerTest.cpp',
             'rendering/RenderOverflowTest.cpp',
             'rendering/shapes/BoxShapeTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }