Cascade declared property values instead of applying values on top of each other

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 912 matching lines @@
             'css/parser/CSSPropertyParser.h',
             'css/parser/MediaQueryBlockWatcher.cpp',
             'css/parser/MediaQueryInputStream.cpp',
             'css/parser/MediaQueryParser.cpp',
             'css/parser/SizesCalcParser.cpp',
             'css/parser/MediaQueryToken.cpp',
             'css/parser/MediaQueryTokenizer.cpp',
             'css/parser/SizesAttributeParser.cpp',
             'css/resolver/AnimatedStyleBuilder.cpp',
             'css/resolver/AnimatedStyleBuilder.h',
+            'css/resolver/CascadedValues.cpp',
+            'css/resolver/CascadedValues.h',
             'css/resolver/CSSToStyleMap.cpp',
             'css/resolver/CSSToStyleMap.h',
             'css/resolver/ElementResolveContext.cpp',
             'css/resolver/ElementResolveContext.h',
             'css/resolver/ElementStyleResources.cpp',
             'css/resolver/ElementStyleResources.h',
             'css/resolver/FilterOperationResolver.cpp',
             'css/resolver/FilterOperationResolver.h',
             'css/resolver/FontBuilder.cpp',
             'css/resolver/FontBuilder.h',
@@ skipping 2497 matching lines @@
             'rendering/RenderTableRowTest.cpp',
             'rendering/shapes/BoxShapeTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'streams/ReadableStreamTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }