Rename FullscreenElementStack to just Fullscreen

Source/core/core.gypi

 {
     'includes': [
       'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/Animation.idl',
             'animation/AnimationEffect.idl',
             'animation/AnimationPlayer.idl',
@@ skipping 2009 matching lines @@
             'dom/ElementFullscreen.cpp',
             'dom/ElementFullscreen.h',
             'dom/ElementRareData.cpp',
             'dom/ElementRareData.h',
             'dom/ElementTraversal.h',
             'dom/EmptyNodeList.cpp',
             'dom/EmptyNodeList.h',
             'dom/ExecutionContext.cpp',
             'dom/ExecutionContext.h',
             'dom/ExecutionContextTask.h',
-            'dom/FullscreenElementStack.cpp',
-            'dom/FullscreenElementStack.h',
+            'dom/Fullscreen.cpp',
+            'dom/Fullscreen.h',
             'dom/GlobalEventHandlers.h',
             'dom/IconURL.cpp',
             'dom/IconURL.h',
             'dom/IdTargetObserver.cpp',
             'dom/IdTargetObserver.h',
             'dom/IdTargetObserverRegistry.cpp',
             'dom/IdTargetObserverRegistry.h',
             'dom/IgnoreDestructiveWriteCountIncrementer.h',
             'dom/IncrementLoadEventDelayCount.cpp',
             'dom/IncrementLoadEventDelayCount.h',
@@ skipping 1421 matching lines @@
             'rendering/shapes/BoxShapeTest.cpp',
             'rendering/style/OutlineValueTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'streams/ReadableStreamTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }