Make EventInterfaces.in build step not depend on bindings generation

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 456 matching lines @@
             'page/WindowPagePopup.idl',
             'svg/SVGDocument.idl',
             'svg/SVGFilterPrimitiveStandardAttributes.idl',
             'svg/SVGFitToViewBox.idl',
             'svg/SVGTests.idl',
             'svg/SVGURIReference.idl',
             'svg/SVGZoomAndPan.idl',
             'workers/AbstractWorker.idl',
             'xml/DocumentXPathEvaluator.idl',
         ],
+        # interfaces that inherit from Event, including Event itself
+        'core_event_idl_files': [
+            'css/CSSFontFaceLoadEvent.idl',
+            'events/ApplicationCacheErrorEvent.idl',
+            'events/AutocompleteErrorEvent.idl',
+            'events/BeforeUnloadEvent.idl',
+            'events/CompositionEvent.idl',
+            'events/CustomEvent.idl',
+            'events/ErrorEvent.idl',
+            'events/Event.idl',
+            'events/FocusEvent.idl',
+            'events/HashChangeEvent.idl',
+            'events/KeyboardEvent.idl',
+            'events/MessageEvent.idl',
+            'events/MouseEvent.idl',
+            'events/MutationEvent.idl',
+            'events/OverflowEvent.idl',
+            'events/PageTransitionEvent.idl',
+            'events/PopStateEvent.idl',
+            'events/ProgressEvent.idl',
+            'events/ResourceProgressEvent.idl',
+            'events/SecurityPolicyViolationEvent.idl',
+            'events/TextEvent.idl',
+            'events/TouchEvent.idl',
+            'events/TransitionEvent.idl',
+            'events/UIEvent.idl',
+            'events/WebKitAnimationEvent.idl',
+            'events/WheelEvent.idl',
+            'html/MediaKeyEvent.idl',
+            'html/canvas/WebGLContextEvent.idl',
+            'html/track/TrackEvent.idl',
+            'speech/SpeechInputEvent.idl',
+            'storage/StorageEvent.idl',
+            'svg/SVGZoomEvent.idl',
+            'xml/XMLHttpRequestProgressEvent.idl',
+        ],
         'webcore_files': [
             'Init.cpp',
             'Init.h',
             'accessibility/AXObjectCache.cpp',
             'accessibility/AXARIAGrid.cpp',
             'accessibility/AXARIAGrid.h',
             'accessibility/AXARIAGridCell.cpp',
             'accessibility/AXARIAGridCell.h',
             'accessibility/AXARIAGridRow.cpp',
             'accessibility/AXARIAGridRow.h',
@@ skipping 2840 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',
         ],
     }
 }