Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

third_party/WebKit/Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/EffectModel.idl',
             'animation/AnimationEffectReadOnly.idl',
@@ skipping 779 matching lines @@
             'layout/shapes/ShapeOutsideInfo.h',
             'style/AppliedTextDecoration.cpp',
             'style/BasicShapes.cpp',
             'style/BorderEdge.cpp',
             'style/BorderEdge.h',
             'style/BorderImageLength.h',
             'style/BorderImageLengthBox.h',
             'style/CachedUAStyle.h',
             'style/ContentData.cpp',
             'style/CounterDirectives.cpp',
+            'style/DataEquivalency.h',
+            'style/DataPersistent.h',
+            'style/DataRef.h',
             'style/FillLayer.cpp',
             'style/GridArea.h',
             'style/GridPositionsResolver.cpp',
             'style/GridPositionsResolver.h',
             'style/ComputedStyle.cpp',
             'style/ComputedStyle.h',
             'style/NinePieceImage.cpp',
             'style/QuotesData.cpp',
             'style/QuotesData.h',
             'style/ShadowData.cpp',
@@ skipping 3294 matching lines @@
             'svg/SVGPathParserTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'workers/WorkerThreadTestHelper.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }