Blink Plugins: Remove Shadow DOM Plugin Placeholder

Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/EffectModel.idl',
             'animation/AnimationEffectReadOnly.idl',
@@ skipping 209 matching lines @@
             'html/ImageData.idl',
             'html/MediaController.idl',
             'html/MediaError.idl',
             'html/MediaKeyError.idl',
             'html/MediaKeyEvent.idl',
             'html/RadioNodeList.idl',
             'html/TextMetrics.idl',
             'html/TimeRanges.idl',
             'html/ValidityState.idl',
             'html/VoidCallback.idl',
-            'html/shadow/PluginPlaceholderElement.idl',
             'html/track/AudioTrack.idl',
             'html/track/AudioTrackList.idl',
             'html/track/TextTrack.idl',
             'html/track/TextTrackCue.idl',
             'html/track/TextTrackCueList.idl',
             'html/track/TextTrackList.idl',
             'html/track/TrackEvent.idl',
             'html/track/VideoTrack.idl',
             'html/track/VideoTrackList.idl',
             'html/track/vtt/VTTCue.idl',
@@ skipping 1768 matching lines @@
             'paint/ThemePainterMac.mm',
             'paint/ThemePainterMac.h',
             'paint/Transform3DRecorder.cpp',
             'paint/Transform3DRecorder.h',
             'paint/TransformRecorder.cpp',
             'paint/TransformRecorder.h',
             'paint/VideoPainter.cpp',
             'paint/VideoPainter.h',
             'paint/ViewPainter.cpp',
             'paint/ViewPainter.h',
-            'plugins/PluginPlaceholder.h',
             'plugins/PluginView.h',
-            'plugins/testing/DictionaryPluginPlaceholder.h',
-            'plugins/testing/DocumentFragmentPluginPlaceholder.h',
             'streams/ReadableByteStream.cpp',
             'streams/ReadableByteStream.h',
             'streams/ReadableByteStreamReader.h',
             'streams/ReadableStream.cpp',
             'streams/ReadableStream.h',
             'streams/ReadableStreamImpl.h',
             'streams/ReadableStreamReader.cpp',
             'streams/ReadableStreamReader.h',
             'streams/Stream.cpp',
             'streams/Stream.h',
@@ skipping 976 matching lines @@
             'html/shadow/MediaControlElementTypes.cpp',
             'html/shadow/MediaControlElementTypes.h',
             'html/shadow/MediaControlElements.cpp',
             'html/shadow/MediaControlElements.h',
             'html/shadow/MediaControls.cpp',
             'html/shadow/MediaControls.h',
             'html/shadow/MeterShadowElement.cpp',
             'html/shadow/MeterShadowElement.h',
             'html/shadow/PickerIndicatorElement.cpp',
             'html/shadow/PickerIndicatorElement.h',
-            'html/shadow/PluginPlaceholderElement.cpp',
-            'html/shadow/PluginPlaceholderElement.h',
             'html/shadow/ProgressShadowElement.cpp',
             'html/shadow/ProgressShadowElement.h',
             'html/shadow/ShadowElementNames.cpp',
             'html/shadow/ShadowElementNames.h',
             'html/shadow/SliderThumbElement.cpp',
             'html/shadow/SliderThumbElement.h',
             'html/shadow/SpinButtonElement.cpp',
             'html/shadow/SpinButtonElement.h',
             'html/shadow/TextControlInnerElements.cpp',
             'html/shadow/TextControlInnerElements.h',
@@ skipping 828 matching lines @@
             'style/OutlineValueTest.cpp',
             'style/SVGComputedStyleTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }