Add a WebDocument::watchCssSelectors(selectors)

Source/core/core.gypi

 {
     'variables': {
         'deprecated_perl_core_idl_files': [
             'css/CSS.idl',
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSKeyframeRule.idl',
@@ skipping 1725 matching lines @@
             'dom/ActiveDOMObject.cpp',
             'dom/Attr.cpp',
             'dom/AutocompleteErrorEvent.h',
             'dom/BeforeLoadEvent.h',
             'dom/BeforeTextInsertedEvent.cpp',
             'dom/BeforeTextInsertedEvent.h',
             'dom/BeforeUnloadEvent.cpp',
             'dom/BeforeUnloadEvent.h',
             'dom/CDATASection.cpp',
             'dom/CDATASection.h',
+            'dom/CSSSelectorWatch.cpp',
             'dom/CharacterData.cpp',
             'dom/CheckedRadioButtons.cpp',
             'dom/ChildListMutationScope.cpp',
             'dom/ChildListMutationScope.h',
             'dom/ChildNodeList.cpp',
             'dom/ChildNodeList.h',
             'dom/ClassNodeList.cpp',
             'dom/ClassNodeList.h',
             'dom/ClientRect.cpp',
             'dom/ClientRect.h',
@@ skipping 2109 matching lines @@
                 'bison_exe': 'bison',
                 # We specify a preprocess so it happens locally and won't get
                 # distributed to goma.
                 # FIXME: /usr/bin/gcc won't exist on OSX forever. We want to
                 # use /usr/bin/clang once we require Xcode 4.x.
                 'preprocessor': '--preprocessor "/usr/bin/gcc -E -P -x c++"'
               }],
          ],
     }
 }