Enable slimming paint for fast/repaint

LayoutTests/platform/linux/fast/repaint/line-flow-with-floats-3-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [372, 383, 48, 80],
         [356, 383, 64, 80],
         [353, 440, 15, 59],
         [352, 380, 2, 19],
         [303, 420, 67, 19],
         [65, 400, 289, 39],
         [65, 380, 304, 59],
         [14, 420, 339, 39],
         [8, 380, 418, 219]
+      ],
+      "paintInvalidationClients": [
+        "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",
+        "InlineTextBox 'shouting \u2018Off with his head!\u2019 or \u2018Off with\n'",
+        "InlineTextBox 'her head!\u2019 about'",
+        "RootInlineBox",
+        "InlineTextBox 'once in a minute.\n'",
+        "RootInlineBox",
+        "InlineTextBox 'Alice began to feel very uneasy: to be sure, she had not as\n'",
+        "InlineTextBox 'yet had'",
+        "RootInlineBox",
+        "InlineTextBox 'any dispute with the Queen, but she knew that it might\n'",
+        "InlineTextBox 'happen any'",
+        "RootInlineBox",
+        "InlineTextBox 'minute, \u2018and then,\u2019 thought she, \u2018what would become of\n'",
+        "InlineTextBox 'me?'",
+        "RootInlineBox",
+        "InlineTextBox 'They\u2019re dreadfully fond of beheading people here; the great'",
+        "RootInlineBox",
+        "InlineTextBox 'wonder is, that there\u2018s any one left alive!\u2019'",
+        "RootInlineBox",
+        "LayoutBlockFlow P",
+        "LayoutText #text",
+        "InlineTextBox 'The players all played at once without waiting'",
+        "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\n'",
+        "InlineTextBox 'her'",
+        "InlineTextBox 'head!\u2019 about once in a minute.\n'"
       ]
     }
   ]
 }