Fix under-invalidation on SVG shape/image resize in subpixels

third_party/WebKit/LayoutTests/paint/invalidation/svg/relative-sized-content-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow div id='contentBox'",
           "rect": [8, 68, 402, 402],
           "reason": "forced by layout"
         },
         {
           "object": "LayoutSVGRect rect id='targetRect'",
           "rect": [9, 69, 400, 400],
-          "reason": "bounds change"
+          "reason": "forced by layout"
         },
         {
           "object": "LayoutSVGRoot svg",
           "rect": [9, 69, 400, 400],
           "reason": "forced by layout"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow div id='contentBox'",
       "reason": "forced by layout"
     },
     {
       "object": "RootInlineBox",
       "reason": "forced by layout"
     },
     {
       "object": "LayoutSVGRoot svg",
       "reason": "forced by layout"
     },
     {
       "object": "LayoutSVGRect rect id='targetRect'",
-      "reason": "bounds change"
+      "reason": "forced by layout"
     }
   ]
 }