[bindings] Remove custom setter used in CSSStyleDeclaration

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 1092 matching lines @@
             'css/CSSRuleList.h',
             'css/CSSSVGDocumentValue.cpp',
             'css/CSSSVGDocumentValue.h',
             'css/CSSSegmentedFontFace.cpp',
             'css/CSSSegmentedFontFace.h',
             'css/CSSSelector.cpp',
             'css/CSSSelectorList.cpp',
             'css/CSSSelectorList.h',
             'css/CSSShadowValue.cpp',
             'css/CSSShadowValue.h',
+            'css/CSSStyleDeclaration.cpp',
             'css/CSSStyleDeclaration.h',
             'css/CSSStyleRule.cpp',
             'css/CSSStyleRule.h',
             'css/CSSStyleSheet.cpp',
             'css/CSSStyleSheet.h',
             'css/CSSSupportsRule.cpp',
             'css/CSSSupportsRule.h',
             'css/CSSTimingFunctionValue.cpp',
             'css/CSSTimingFunctionValue.h',
             'css/CSSToLengthConversionData.cpp',
@@ skipping 2743 matching lines @@
             'paint/LayerClipRecorderTest.cpp',
             'paint/LayoutObjectDrawingRecorderTest.cpp',
             'paint/TextPainterTest.cpp',
             'streams/ReadableStreamReaderTest.cpp',
             'streams/ReadableStreamTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }