Simplify Custom Element constructors to be functions, not wrappers

Source/core/core.gypi

 {
     'variables': {
         'core_idl_files': [
             'css/CSS.idl',
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSMediaRule.idl',
@@ skipping 32 matching lines @@
             'dom/Attr.idl',
             'dom/AutocompleteErrorEvent.idl',
             'dom/BeforeLoadEvent.idl',
             'dom/CDATASection.idl',
             'dom/CharacterData.idl',
             'dom/ClientRect.idl',
             'dom/ClientRectList.idl',
             'dom/Clipboard.idl',
             'dom/Comment.idl',
             'dom/CompositionEvent.idl',
-            'dom/CustomElementConstructor.idl',
             'dom/CustomEvent.idl',
             'dom/DOMCoreException.idl',
             'dom/DOMError.idl',
             'dom/DOMImplementation.idl',
             'dom/DOMStringList.idl',
             'dom/DOMStringMap.idl',
             'dom/DataTransferItem.idl',
             'dom/DataTransferItemList.idl',
             'dom/DeviceOrientationEvent.idl',
             'dom/Document.idl',
@@ skipping 1627 matching lines @@
             'dom/Comment.h',
             'dom/CompositionEvent.cpp',
             'dom/CompositionEvent.h',
             'dom/ContainerNode.cpp',
             'dom/ContainerNodeAlgorithms.h',
             'dom/ContainerNodeAlgorithms.cpp',
             'dom/ContextDestructionObserver.cpp',
             'dom/ContextFeatures.cpp',
             'dom/ContextFeatures.h',
             'dom/CrossThreadTask.h',
-            'dom/CustomElementConstructor.cpp',
-            'dom/CustomElementConstructor.h',
             'dom/CustomElementDefinition.cpp',
             'dom/CustomElementDefinition.h',
             'dom/CustomElementRegistry.cpp',
             'dom/CustomElementRegistry.h',
             'dom/CustomElementUpgradeCandidateMap.cpp',
             'dom/CustomElementUpgradeCandidateMap.h',
             'dom/CustomEvent.cpp',
             'dom/CustomEvent.h',
             'dom/DOMCoreException.cpp',
             'dom/DOMCoreException.h',
@@ skipping 1987 matching lines @@
                 'bison_exe': 'bison',
                 # We specify a preprocess so it happens locally and won't get
                 # distributed to goma.
                 # FIXME: /usr/bin/gcc won't exist on OSX forever. We want to
                 # use /usr/bin/clang once we require Xcode 4.x.
                 'preprocessor': '--preprocessor "/usr/bin/gcc -E -P -x c++"'
               }],
          ],
     }
 }