Fix gradient background invalidation when HTML size changes

third_party/WebKit/LayoutTests/virtual/disable-spinvalidation/paint/invalidation/shift-relative-positioned-container-with-image-addition-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [785, 829],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
-          "object": "LayoutBlockFlow HTML",
-          "rect": [0, 0, 785, 829],
-          "reason": "forced by layout"
-        },
-        {
           "object": "LayoutView #document",
           "rect": [0, 735, 785, 94],
           "reason": "incremental"
         },
         {
           "object": "LayoutBlockFlow (relative positioned) DIV class='relative paddingTop'",
           "rect": [8, 180, 769, 641],
           "reason": "bounds change"
         },
         {
           "object": "LayoutBlockFlow (relative positioned) DIV class='relative paddingTop'",
           "rect": [8, 86, 769, 641],
           "reason": "bounds change"
         },
         {
           "object": "LayoutIFrame IFRAME id='iframe'",
           "rect": [8, 86, 732, 94],
           "reason": "layoutObject insertion"
         },
         {
-          "object": "LayoutBlockFlow HTML",
-          "rect": [10, 88, 728, 90],
-          "reason": "forced by layout"
-        },
-        {
           "object": "LayoutImage IMG",
           "rect": [58, 230, 489, 537],
           "reason": "bounds change"
         },
         {
           "object": "LayoutImage IMG",
           "rect": [58, 136, 489, 537],
           "reason": "bounds change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutView #document",
       "reason": "incremental"
     },
     {
-      "object": "LayoutBlockFlow HTML",
-      "reason": "forced by layout"
-    },
-    {
       "object": "LayoutIFrame IFRAME id='iframe'",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutBlockFlow (relative positioned) DIV class='relative paddingTop'",
       "reason": "bounds change"
     },
     {
       "object": "RootInlineBox",
       "reason": "bounds change"
@@ skipping 13 matching lines @@
     {
       "object": "LayoutView #document",
       "reason": "scroll"
     },
     {
       "object": "LayoutView #document",
       "reason": "location change"
     },
     {
       "object": "LayoutBlockFlow HTML",
-      "reason": "forced by layout"
+      "reason": "location change"
     },
     {
       "object": "LayoutBlockFlow BODY",
       "reason": "location change"
     }
   ]
 }