Don't invalidate rect if it's covered by fully invalidated parent's visual rect

third_party/WebKit/LayoutTests/platform/mac-mac10.9/paint/invalidation/multi-layout-one-frame-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV id='inner-editor'",
           "rect": [138, 11, 117, 13],
           "reason": "forced by layout"
         },
         {
           "object": "LayoutBlockFlow DIV id='inner-editor'",
           "rect": [11, 11, 117, 13],
           "reason": "forced by layout"
-        },
-        {
-          "object": "LayoutText #text",
-          "rect": [138, 11, 40, 13],
-          "reason": "full"
-        },
-        {
-          "object": "LayoutText #text",
-          "rect": [11, 11, 40, 13],
-          "reason": "full"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow DIV id='inner-editor'",
       "reason": "forced by layout"
     },
     {
@@ skipping 20 matching lines @@
       "object": "LayoutText #text",
       "reason": "full"
     },
     {
       "object": "InlineTextBox 'PASSED'",
       "reason": "full"
     }
   ]
 }