Use Shadow DOM to display fallback content for images

LayoutTests/platform/linux/tables/mozilla/bugs/bug215629-expected.txt

Index: LayoutTests/platform/linux/tables/mozilla/bugs/bug215629-expected.txt
diff --git a/LayoutTests/platform/linux/tables/mozilla/bugs/bug215629-expected.txt b/LayoutTests/platform/linux/tables/mozilla/bugs/bug215629-expected.txt
index 65b8a6bf59150c9a4a4485c45d62fd570ff48bd4..d44ae265e3190f0601485d36968b978159ceb1b3 100644
--- a/LayoutTests/platform/linux/tables/mozilla/bugs/bug215629-expected.txt
+++ b/LayoutTests/platform/linux/tables/mozilla/bugs/bug215629-expected.txt
@@ -10,10 +10,10 @@ layer at (0,0) size 800x600
         RenderTableSection {TBODY} at (0,0) size 732x57
           RenderTableRow {TR} at (0,2) size 732x53
             RenderTableCell {TD} at (2,2) size 728x53 [r=0 c=0 rs=1 cs=1]
-              RenderImage {IMG} at (1,1) size 167x51
-              RenderImage {IMG} at (168,1) size 181x51
-              RenderImage {IMG} at (349,1) size 205x51
-              RenderImage {IMG} at (554,1) size 173x51
+              RenderBlock {IMG} at (1,1) size 167x51
+              RenderBlock {IMG} at (168,1) size 181x51
+              RenderBlock {IMG} at (349,1) size 205x51
+              RenderBlock {IMG} at (554,1) size 173x51
       RenderBlock {P} at (0,109) size 784x20
         RenderText {#text} at (0,0) size 434x19
           text run at (0,0) width 434: "Identical to the above except that width=\"100%\" was removed from TD"
@@ -21,7 +21,31 @@ layer at (0,0) size 800x600
         RenderTableSection {TBODY} at (0,0) size 732x57
           RenderTableRow {TR} at (0,2) size 732x53
             RenderTableCell {TD} at (2,2) size 728x53 [r=0 c=0 rs=1 cs=1]
-              RenderImage {IMG} at (1,1) size 167x51
-              RenderImage {IMG} at (168,1) size 181x51
-              RenderImage {IMG} at (349,1) size 205x51
-              RenderImage {IMG} at (554,1) size 173x51
+              RenderBlock {IMG} at (1,1) size 167x51
+              RenderBlock {IMG} at (168,1) size 181x51
+              RenderBlock {IMG} at (349,1) size 205x51
+              RenderBlock {IMG} at (554,1) size 173x51
+layer at (11,47) size 167x51 clip at (12,48) size 165x49
+  RenderBlock {DIV} at (0,0) size 167x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (178,47) size 181x51 clip at (179,48) size 179x49
+  RenderBlock {DIV} at (0,0) size 181x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (359,47) size 205x51 clip at (360,48) size 203x49
+  RenderBlock {DIV} at (0,0) size 205x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (564,47) size 173x51 clip at (565,48) size 171x49
+  RenderBlock {DIV} at (0,0) size 173x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (11,156) size 167x51 clip at (12,157) size 165x49
+  RenderBlock {DIV} at (0,0) size 167x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (178,156) size 181x51 clip at (179,157) size 179x49
+  RenderBlock {DIV} at (0,0) size 181x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (359,156) size 205x51 clip at (360,157) size 203x49
+  RenderBlock {DIV} at (0,0) size 205x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (564,156) size 173x51 clip at (565,157) size 171x49
+  RenderBlock {DIV} at (0,0) size 173x51 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16