Harmonize FilterEffect::mapRect and mapPaintRect

third_party/WebKit/LayoutTests/paint/invalidation/filters/effect-reference-repaint-gaussianblur-xonly-expected.txt

 {
   "name": "Content Root Layer",
   "bounds": [800, 600],
   "children": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV class='box'",
-          "rect": [1, 50, 314, 200],
+          "rect": [38, 50, 240, 200],
           "reason": "style change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow DIV class='box'",
       "reason": "style change"
     }
   ]
 }