[Line Layout API] Add shim for Paint objects to access underlying LayoutObject

Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/EffectModel.idl',
             'animation/AnimationEffectReadOnly.idl',
@@ skipping 1910 matching lines @@
             'paint/InlinePainter.h',
             'paint/InlineTextBoxPainter.cpp',
             'paint/InlineTextBoxPainter.h',
             'paint/LayerClipRecorder.cpp',
             'paint/LayerClipRecorder.h',
             'paint/LayerFixedPositionRecorder.cpp',
             'paint/LayerFixedPositionRecorder.h',
             'paint/LayoutObjectDrawingRecorder.h',
             'paint/LineBoxListPainter.cpp',
             'paint/LineBoxListPainter.h',
+            'paint/LineLayoutPaintShim.h',

[leviw_travelin_and_unemployed, 2015/08/26 17:54:04]

I was thinking, we may end up needing this in another directory if we want to
enforce blocking it from being imported into Line Layout code.

             'paint/ListItemPainter.cpp',
             'paint/ListItemPainter.h',
             'paint/ListMarkerPainter.cpp',
             'paint/ListMarkerPainter.h',
             'paint/MediaControlsPainter.cpp',
             'paint/MediaControlsPainter.h',
             'paint/MultiColumnSetPainter.cpp',
             'paint/MultiColumnSetPainter.h',
             'paint/NinePieceImageGrid.cpp',
             'paint/NinePieceImageGrid.h',
@@ skipping 1914 matching lines @@
             'style/OutlineValueTest.cpp',
             'style/SVGComputedStyleTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }