Let StyleResolver figure out differences between UA style and resolved style.

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/AnimationNode.idl',
@@ skipping 1895 matching lines @@
             'rendering/style/StyleMotionData.h',
             'rendering/style/StyleMotionPath.h',
             '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/style/UAStyleChange.h',
             'storage/DOMWindowStorage.cpp',
             'storage/DOMWindowStorage.h',
             'storage/DOMWindowStorageController.cpp',
             'storage/DOMWindowStorageController.h',
             'storage/Storage.cpp',
             'storage/Storage.h',
             'storage/StorageArea.cpp',
             'storage/StorageArea.h',
             'storage/StorageEvent.cpp',
             'storage/StorageEvent.h',
@@ skipping 1837 matching lines @@
             'rendering/style/RenderStyleTest.cpp',
             'rendering/style/SVGRenderStyleTest.cpp',
             'streams/ReadableStreamTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }