Use Shadow DOM to display fallback content for images

LayoutTests/platform/linux/fast/table/007-expected.txt

Index: LayoutTests/platform/linux/fast/table/007-expected.txt
diff --git a/LayoutTests/platform/linux/fast/table/007-expected.txt b/LayoutTests/platform/linux/fast/table/007-expected.txt
index 224ce4276b02d1c5b1118a84379581738ca66e3e..67f37f5b5430edf1bbd949dca5bb51a6f0be8fab 100644
--- a/LayoutTests/platform/linux/fast/table/007-expected.txt
+++ b/LayoutTests/platform/linux/fast/table/007-expected.txt
@@ -7,7 +7,7 @@ layer at (0,0) size 800x600
         RenderTableSection {TBODY} at (1,1) size 522x92
           RenderTableRow {TR} at (0,0) size 522x48
             RenderTableCell {TD} at (0,0) size 27x3 [border: (1px inset #808080)] [r=0 c=0 rs=3 cs=1]
-              RenderImage {IMG} at (1,1) size 25x1
+              RenderBlock {IMG} at (1,1) size 25x1
             RenderTableCell {TD} at (27,0) size 495x22 [border: (1px inset #808080)] [r=0 c=1 rs=1 cs=1]
               RenderText {#text} at (1,1) size 20x19
                 text run at (1,1) width 20: "foo"
@@ -24,3 +24,6 @@ layer at (0,0) size 800x600
             RenderTableCell {TD} at (0,70) size 522x22 [border: (1px inset #808080)] [r=3 c=0 rs=1 cs=2]
               RenderText {#text} at (1,1) size 23x19
                 text run at (1,1) width 23: "goo"
+layer at (10,10) size 25x4 clip at (11,11) size 23x2 scrollHeight 18
+  RenderBlock {DIV} at (0,0) size 25x4 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16