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

third_party/WebKit/LayoutTests/paint/invalidation/bugzilla-6473-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
-          "object": "LayoutBlockFlow DIV id='im'",
-          "rect": [11, 131, 100, 100],
-          "reason": "forced by layout"
-        },
-        {
-          "object": "LayoutText #text",
-          "rect": [11, 131, 4, 19],
-          "reason": "forced by layout"
+          "object": "LayoutBlockFlow DIV id='allcontent'",
+          "rect": [8, 130, 784, 50],
+          "reason": "style change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
-      "object": "LayoutBlockFlow DIV id='im'",
+      "object": "LayoutBlockFlow DIV id='allcontent'",
+      "reason": "style change"
+    },
+    {
+      "object": "LayoutBlockFlow (relative positioned) P",
       "reason": "forced by layout"
     },
     {
       "object": "RootInlineBox",
       "reason": "forced by layout"
     },
     {
       "object": "LayoutText #text",
       "reason": "forced by layout"
     },
     {
-      "object": "InlineTextBox '\u00A0'",
+      "object": "InlineTextBox 'SUCCESS'",
       "reason": "forced by layout"
     }
   ]
 }