Enable slimming paint for fast/repaint

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

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [303, 420, 67, 19],
         [275, 420, 65, 19],
         [134, 360, 132, 19],
         [118, 360, 132, 19],
         [65, 380, 304, 59],
         [65, 380, 287, 19],
         [49, 380, 320, 59],
         [49, 380, 303, 19],
         [46, 363, 16, 64],
         [14, 440, 354, 59],
         [14, 420, 355, 79],
         [8, 360, 418, 99]
+      ],
+      "paintInvalidationClients": [
+        "InlineTextBox 'was a very\n'",
+        "InlineTextBox 'difficult game indeed.\n'",
+        "RootInlineBox",
+        "InlineTextBox 'The players all played at once without waiting\n'",
+        "InlineTextBox 'for'",
+        "RootInlineBox",
+        "InlineTextBox 'turns,\n'",
+        "InlineTextBox 'quarrelling all the while, and fighting for the'",
+        "RootInlineBox",
+        "InlineTextBox 'hedgehogs; and in\n'",
+        "InlineTextBox 'a very short time '",
+        "InlineTextBox 'the Queen'",
+        "RootInlineBox",
+        "InlineTextBox 'was in a furious passion, and went\n'",
+        "InlineTextBox 'stamping about, and'",
+        "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 the'",
+        "InlineTextBox 'hedgehogs; and in\n'",
+        "InlineTextBox 'a very short time '",
+        "LayoutText #text",
+        "InlineTextBox 'the Queen'",
+        "LayoutText #text",
+        "InlineTextBox ' was'",
+        "InlineTextBox 'in a furious passion, and went\n'",
+        "InlineTextBox 'stamping about, and'",
+        "InlineTextBox 'shouting \u2018Off with his head!\u2019 or \u2018Off with\n'",
+        "InlineTextBox 'her head!\u2019 about'",
+        "InlineTextBox 'once in a minute.\n'"
       ]
     }
   ]
 }