Tweak PaintInvalidationReasons

third_party/WebKit/LayoutTests/paint/invalidation/repaint-composited-child-in-scrolled-container-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow (positioned) DIV id='outer'",
           "rect": [8, 293, 285, 15],
-          "reason": "scroll"
+          "reason": "scroll control"
         }
       ]
     },
     {
       "name": "Ancestor Clipping Layer",
       "position": [8, 8],
       "bounds": [285, 285],
       "shouldFlattenTransform": false
     },
     {
       "name": "LayoutBlockFlow (positioned) DIV id='container'",
       "position": [-315, 0],
       "bounds": [600, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "backgroundColor": "#FF0000",
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV id='inner'",
           "rect": [0, 0, 600, 600],
           "reason": "style change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "HorizontalScrollbar",
-      "reason": "scroll"
+      "reason": "scroll control"
     },
     {
       "object": "LayoutBlockFlow DIV id='inner'",
       "reason": "style change"
     }
   ]
 }