Enable slimming paint for fast/repaint

LayoutTests/platform/win/fast/repaint/line-flow-with-floats-2-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [372, 374, 48, 80],
         [372, 371, 48, 80],
         [65, 389, 303, 33],
         [65, 386, 303, 36],
         [14, 475, 355, 3],
         [14, 407, 355, 33],
         [14, 404, 355, 36],
         [14, 356, 48, 64],
         [14, 353, 48, 64],
         [14, 188, 45, 20],
         [14, 188, 41, 17],
         [13, 190, 408, 72],
         [13, 188, 408, 71],
         [8, 572, 418, 3],
         [8, 569, 418, 6],
         [8, 170, 418, 399]
+      ],
+      "paintInvalidationClients": [
+        "InlineTextBox 'going to give the hedgehog a blow with its head, it'",
+        "RootInlineBox",
+        "InlineTextBox ''",
+        "InlineTextBox ' twist itself round and look up in her face, with\n'",
+        "InlineTextBox 'such a'",
+        "RootInlineBox",
+        "LayoutBlockFlow P",
+        "LayoutBlockFlow P",
+        "LayoutInline I id='would'",
+        "LayoutText #text",
+        "InlineTextBox 'would'",
+        "LayoutText #text",
+        "InlineTextBox ' twist itself round and look up in her face, with\n'",
+        "InlineTextBox 'such a'",
+        "InlineTextBox 'puzzled expression that she could not help bursting out'",
+        "InlineTextBox 'laughing: and when she had got its head down, and was going'",
+        "InlineTextBox 'to\n'",
+        "LayoutBlockFlow (floating) SPAN id='blueFloat'",
+        "LayoutBlockFlow (floating) SPAN id='greenFloat'",
+        "LayoutText #text",
+        "InlineTextBox 'for turns,\n'",
+        "InlineTextBox 'quarrelling all the while, and fighting'",
+        "InlineTextBox 'for the hedgehogs; and in\n'",
+        "InlineTextBox 'a very short time '",
+        "LayoutText #text",
+        "InlineTextBox 'the'",
+        "InlineTextBox 'Queen'",
+        "LayoutText #text",
+        "InlineTextBox ' was in a furious passion, and went\n'",
+        "InlineTextBox 'stamping'",
+        "InlineTextBox 'about, and shouting \u2018Off with his head!\u2019 or \u2018Off with'",
+        "InlineTextBox 'her head!\u2019 about once in a minute.\n'"
       ]
     }
   ]
 }