Revert r154797: "Move isValid/isCurrentColor from Color to StyleColor"

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 720 matching lines @@
             'css/SVGCSSParser.cpp',
             'css/SelectorChecker.cpp',
             'css/SelectorChecker.h',
             'css/SelectorCheckerFastPath.cpp',
             'css/SelectorCheckerFastPath.h',
             'css/SelectorFilter.cpp',
             'css/SelectorFilter.h',
             'css/ShadowValue.cpp',
             'css/ShadowValue.h',
             'css/SiblingTraversalStrategies.h',
-            'css/StyleColor.cpp',
             'css/StyleColor.h',
             'css/StyleInvalidationAnalysis.cpp',
             'css/StyleInvalidationAnalysis.h',
             'css/StyleMedia.cpp',
             'css/StyleMedia.h',
             'css/StylePropertySerializer.cpp',
             'css/StylePropertySerializer.h',
             'css/StylePropertySet.cpp',
             'css/StylePropertySet.h',
             'css/StylePropertyShorthandCustom.cpp',
@@ skipping 3117 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++"'
               }],
          ],
     }
 }