Enable slimming paint for fast/repaint

LayoutTests/fast/repaint/line-flow-with-floats-5-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [178, 350, 146, 18],
         [162, 350, 146, 18],
         [65, 386, 303, 36],
         [65, 368, 304, 18],
         [49, 368, 321, 54],
         [49, 368, 301, 18],
         [46, 353, 16, 64],
         [8, 350, 418, 72]
+      ],
+      "paintInvalidationClients": [
+        "InlineTextBox 'that it was a very\n'",
+        "InlineTextBox 'difficult game indeed.\n'",
+        "RootInlineBox",
+        "InlineTextBox 'The players all played at once without waiting'",
+        "RootInlineBox",
+        "InlineTextBox 'for turns,\n'",
+        "InlineTextBox 'quarrelling all the while, and fighting'",
+        "RootInlineBox",
+        "InlineTextBox 'for the hedgehogs; and in\n'",
+        "InlineTextBox 'a very short time '",
+        "InlineTextBox 'the'",
+        "RootInlineBox",
+        "LayoutBlockFlow P",
+        "LayoutBlockFlow (floating) SPAN id='blueFloat'",
+        "LayoutText #text",
+        "InlineTextBox 'difficult game indeed.\n'",
+        "LayoutText #text",
+        "InlineTextBox 'The players all played at once without waiting\n'",
+        "LayoutText #text",
+        "InlineTextBox 'for'",
+        "InlineTextBox 'turns,\n'",
+        "InlineTextBox 'quarrelling all the while, and fighting for'",
+        "InlineTextBox 'the hedgehogs; and in\n'",
+        "InlineTextBox 'a very short time '"
       ]
     }
   ]
 }