Track reasons for |Node::SetNeedsStyleRecalc|

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 2136 matching lines @@
             'dom/SecurityContext.h',
             'dom/SelectorQuery.cpp',
             'dom/SelectorQuery.h',
             'dom/ShadowTreeStyleSheetCollection.cpp',
             'dom/ShadowTreeStyleSheetCollection.h',
             'dom/SimulatedClickOptions.h',
             'dom/SpaceSplitString.cpp',
             'dom/StaticNodeList.h',
             'dom/StringCallback.cpp',
             'dom/StringCallback.h',
+            'dom/StyleChangeReason.cpp',
+            'dom/StyleChangeReason.h',
             'dom/StyleElement.cpp',
             'dom/StyleElement.h',
             'dom/StyleEngine.cpp',
             'dom/StyleEngine.h',
             'dom/StyleSheetCandidate.cpp',
             'dom/StyleSheetCandidate.h',
             'dom/StyleSheetCollection.cpp',
             'dom/StyleSheetCollection.h',
             'dom/TagCollection.cpp',
             'dom/TagCollection.h',
@@ skipping 1371 matching lines @@
             'rendering/shapes/BoxShapeTest.cpp',
             'rendering/style/OutlineValueTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'streams/ReadableStreamTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }