Enable slimming paint for fast/repaint

LayoutTests/platform/mac/fast/repaint/line-flow-with-floats-10-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [369, 422, 1, 54],
         [65, 404, 304, 36],
         [14, 404, 355, 36],
         [14, 364, 48, 64],
         [14, 353, 48, 64],
         [8, 350, 418, 126]
+      ],
+      "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",
+        "InlineTextBox 'Queen'",
+        "InlineTextBox ' was in a furious passion, and went\n'",
+        "InlineTextBox 'stamping'",
+        "RootInlineBox",
+        "InlineTextBox 'about, and shouting \u2018Off with his head!\u2019 or \u2018Off with'",
+        "RootInlineBox",
+        "InlineTextBox 'her head!\u2019 about once in a minute.\n'",
+        "RootInlineBox",
+        "LayoutBlockFlow P",
+        "LayoutBlockFlow (floating) SPAN id='blueFloat'",
+        "LayoutText #text",
+        "InlineTextBox 'the'",
+        "InlineTextBox 'Queen'",
+        "LayoutText #text",
+        "InlineTextBox ' was in a furious passion, and went'",
+        "InlineTextBox 'stamping about, and shouting \u2018Off with his head!\u2019 or'",
+        "InlineTextBox '\u2018Off with\n'",
+        "InlineTextBox 'her head!\u2019 about once in a minute.\n'"
       ]
     }
   ]
 }