Add infrastructure for partial layouts

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 1315 matching lines @@
             'rendering/InlineBox.cpp',
             'rendering/InlineFlowBox.cpp',
             'rendering/InlineIterator.h',
             'rendering/InlineTextBox.cpp',
             'rendering/ImageQualityController.h',
             'rendering/ImageQualityController.cpp',
             'rendering/LayoutState.cpp',
             'rendering/OrderIterator.cpp',
             'rendering/OrderIterator.h',
             'rendering/LayoutRepainter.cpp',
+            'rendering/PartialLayoutState.h',
             'rendering/Pagination.cpp',
             'rendering/Pagination.h',
             'rendering/PointerEventsHitRules.cpp',
             'rendering/PointerEventsHitRules.h',
             'rendering/RenderApplet.cpp',
             'rendering/RenderApplet.h',
             'rendering/RenderBR.cpp',
             'rendering/RenderBlock.cpp',
             'rendering/RenderBlockLineLayout.cpp',
             'rendering/RenderBox.cpp',
@@ skipping 2498 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++"'
               }],
          ],
     }
 }