Move GridCoordinate and GridSpan to a separate file

Source/core/core.gypi

 {
     'variables': {
         'core_idl_files': [
             'css/CSS.idl',
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSMediaRule.idl',
@@ skipping 1472 matching lines @@
             'rendering/shapes/ShapeInsideInfo.cpp',
             'rendering/shapes/ShapeInsideInfo.h',
             'rendering/shapes/ShapeInterval.cpp',
             'rendering/shapes/ShapeInterval.h',
             'rendering/shapes/ShapeOutsideInfo.cpp',
             'rendering/shapes/ShapeOutsideInfo.h',
             'rendering/style/BasicShapes.cpp',
             'rendering/style/ContentData.cpp',
             'rendering/style/CounterDirectives.cpp',
             'rendering/style/FillLayer.cpp',
+            'rendering/style/GridCoordinate.h',
             'rendering/style/KeyframeList.cpp',
             'rendering/style/KeyframeList.h',
             'rendering/style/NinePieceImage.cpp',
             'rendering/style/QuotesData.cpp',
             'rendering/style/QuotesData.h',
             'rendering/style/RenderStyle.cpp',
             'rendering/style/ShadowData.cpp',
             'rendering/style/StyleBackgroundData.cpp',
             'rendering/style/StyleBoxData.cpp',
             'rendering/style/StyleCachedImage.cpp',
@@ skipping 2205 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++"'
               }],
          ],
     }
 }