Blink Plugins: Remove Shadow DOM Plugin Placeholder remnants.

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 3597 matching lines @@
             '<(blink_core_output_dir)/html/track/TrackEventInit.cpp',
             '<(blink_core_output_dir)/html/track/TrackEventInit.h',
             '<(blink_core_output_dir)/input/InputDeviceCapabilitiesInit.cpp',
             '<(blink_core_output_dir)/input/InputDeviceCapabilitiesInit.h',
             '<(blink_core_output_dir)/page/EventSourceInit.cpp',
             '<(blink_core_output_dir)/page/EventSourceInit.h',
         ],
         'core_testing_dictionary_idl_files': [
             'testing/InternalDictionary.idl',
             'testing/InternalDictionaryDerived.idl',
-            'testing/PluginPlaceholderOptions.idl',
         ],
         'webcore_testing_idl_files': [
             'testing/DictionaryTest.idl',
             'testing/GCObservation.idl',
             'testing/GarbageCollectedScriptWrappable.idl',
             'testing/InternalSettings.idl',
             'testing/LayerRect.idl',
             'testing/LayerRectList.idl',
             'testing/PrivateScriptTest.idl',
             'testing/RefCountedScriptWrappable.idl',
             'testing/TypeConversions.idl',
             'testing/UnionTypesTest.idl',
         ],
         # testing IDL files that have partial interfaces in modules.
         'webcore_testing_idl_with_modules_dependency_files': [
             'testing/Internals.idl',
         ],
         'webcore_testing_dependency_idl_files': [
             'testing/PartialPrivateScriptTest.idl',
         ],
         'generated_webcore_testing_idl_files': [
             '<(blink_core_output_dir)/testing/InternalRuntimeFlags.idl',
             '<(blink_core_output_dir)/testing/InternalSettingsGenerated.idl',
         ],
         'generated_core_testing_dictionary_files': [
             '<(blink_core_output_dir)/testing/InternalDictionary.cpp',
             '<(blink_core_output_dir)/testing/InternalDictionary.h',
             '<(blink_core_output_dir)/testing/InternalDictionaryDerived.cpp',
             '<(blink_core_output_dir)/testing/InternalDictionaryDerived.h',
-            '<(blink_core_output_dir)/testing/PluginPlaceholderOptions.cpp',
-            '<(blink_core_output_dir)/testing/PluginPlaceholderOptions.h',
         ],
         'webcore_testing_files': [
             '<(blink_core_output_dir)/testing/InternalSettingsGenerated.cpp',
             '<(blink_core_output_dir)/testing/InternalSettingsGenerated.h',
             'testing/CoreTestPrinters.cpp',
             'testing/DictionaryTest.cpp',
             'testing/DictionaryTest.h',
             'testing/DummyPageHolder.cpp',
             'testing/DummyPageHolder.h',
             'testing/GCObservation.cpp',
@@ skipping 193 matching lines @@
             'style/OutlineValueTest.cpp',
             'style/SVGComputedStyleTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }