Introduce Layout*::adjustVisualRectForRasterEffects and use it for SVG hairlines.

third_party/WebKit/LayoutTests/paint/invalidation/svg/path-pathlength-change-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutSVGPath path",
-          "rect": [98, 98, 120, 120],
+          "rect": [97, 97, 122, 122],
           "reason": "full"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutSVGPath path",
       "reason": "full"
     }
   ]
 }