Need to repaint its ::first-line background when a block moves.

third_party/WebKit/LayoutTests/platform/linux/fast/repaint/paint-invalidation-with-reparent-across-frame-boundaries-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [18, 18, 284, 20],
         [18, 18, 284, 20],
         [18, 18, 22, 19],
         [8, 187, 784, 20],
         [8, 187, 22, 19]
       ],
       "paintInvalidationClients": [
         "InlineTextBox 'abc'",
         "LayoutText #text",
         "RootInlineBox",
         "LayoutBlockFlow DIV id='inner-target'",
         "LayoutBlockFlow BODY",
         "LayoutBlockFlow DIV id='inner-target'",
+        "RootInlineBox",
         "LayoutText #text",
         "InlineTextBox 'abc'"
       ]
     }
   ]
 }