Paint invalidation of local attachment backgrounds

third_party/WebKit/LayoutTests/paint/invalidation/composited-overflow-with-local-background-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
       "name": "LayoutBlockFlow DIV id='scroller'",
@@ skipping 17 matching lines @@
     },
     {
       "name": "Scrolling Contents Layer",
       "bounds": [185, 300],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV id='scroller'",
           "rect": [0, 0, 185, 300],
-          "reason": "style change"
+          "reason": "background on scrolling contents layer"
         }
       ]
     },
     {
       "name": "Overflow Controls Host Layer",
       "bounds": [200, 200]
     },
     {
       "name": "Horizontal Scrollbar Layer",
       "position": [0, 185],
       "bounds": [185, 15]
     },
     {
       "name": "Vertical Scrollbar Layer",
       "position": [185, 0],
       "bounds": [15, 185]
     },
     {
       "name": "Scroll Corner Layer",
       "position": [185, 185],
       "bounds": [15, 15],
       "drawsContent": true
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "Scrolling Contents Layer",
-      "reason": "style change"
+      "reason": "background on scrolling contents layer"
     },
     {
       "object": "LayoutBlockFlow DIV id='scroller'",
       "reason": "style change"
     }
   ]
 }