Implement 'will-change' parsing

Source/core/core.gypi

 {
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/Animation.idl',
             'animation/Player.idl',
             'animation/TimedItem.idl',
             'animation/Timeline.idl',
             'animation/Timing.idl',
             'clipboard/Clipboard.idl',
@@ skipping 1613 matching lines @@
             'rendering/style/StyleGridItemData.cpp',
             'rendering/style/StyleInheritedData.cpp',
             'rendering/style/StyleMarqueeData.cpp',
             'rendering/style/StyleMultiColData.cpp',
             'rendering/style/StylePendingImage.h',
             'rendering/style/StyleRareInheritedData.cpp',
             'rendering/style/StyleRareNonInheritedData.cpp',
             'rendering/style/StyleSurroundData.cpp',
             'rendering/style/StyleTransformData.cpp',
             'rendering/style/StyleVisualData.cpp',
+            'rendering/style/StyleWillChangeData.cpp',
             'rendering/svg/SVGInlineFlowBox.cpp',
             'rendering/svg/SVGInlineFlowBox.h',
             'rendering/svg/SVGInlineTextBox.cpp',
             'rendering/svg/SVGInlineTextBox.h',
             'rendering/svg/SVGMarkerData.h',
             'rendering/svg/SVGPathData.cpp',
             'rendering/svg/SVGPathData.h',
             'rendering/svg/SVGRenderSupport.cpp',
             'rendering/svg/SVGRenderSupport.h',
             'rendering/svg/SVGRenderTreeAsText.cpp',
@@ skipping 1612 matching lines @@
             'html/parser/HTMLParserThreadTest.cpp',
             'html/track/vtt/BufferedLineReaderTest.cpp',
             'html/track/vtt/VTTScannerTest.cpp',
             'rendering/RenderOverflowTest.cpp',
             'rendering/shapes/BoxShapeTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
         ],
     }
 }