Use Shadow DOM to display fallback content for images

LayoutTests/platform/linux/tables/mozilla/bugs/bug3977-expected.txt

Index: LayoutTests/platform/linux/tables/mozilla/bugs/bug3977-expected.txt
diff --git a/LayoutTests/platform/linux/tables/mozilla/bugs/bug3977-expected.txt b/LayoutTests/platform/linux/tables/mozilla/bugs/bug3977-expected.txt
index fdf837665ee7601fa603276ece85d83d96d3fce5..a129823e90dd45c7708362c175d20c9e166a4611 100644
--- a/LayoutTests/platform/linux/tables/mozilla/bugs/bug3977-expected.txt
+++ b/LayoutTests/platform/linux/tables/mozilla/bugs/bug3977-expected.txt
@@ -7,7 +7,7 @@ layer at (0,0) size 785x965
         RenderTableSection {TBODY} at (1,1) size 598x263
           RenderTableRow {TR} at (0,2) size 598x77
             RenderTableCell {TD} at (2,2) size 594x77 [border: (1px inset #808080)] [r=0 c=0 rs=1 cs=3]
-              RenderImage {IMG} at (2,2) size 590x73
+              RenderBlock {IMG} at (2,2) size 590x73
               RenderText {#text} at (0,0) size 0x0
           RenderTableRow {TR} at (0,81) size 598x96
             RenderTableCell {TD} at (2,81) size 114x24 [bgcolor=#94BD73] [border: (1px inset #808080)] [r=1 c=0 rs=1 cs=1]
@@ -28,11 +28,11 @@ layer at (0,0) size 785x965
                   text run at (0,0) width 68: "etc., etc. ..."
           RenderTableRow {TR} at (0,179) size 598x37
             RenderTableCell {TD} at (2,179) size 594x37 [border: (1px inset #808080)] [r=2 c=0 rs=1 cs=3]
-              RenderImage {IMG} at (2,2) size 589x33
+              RenderBlock {IMG} at (2,2) size 589x33
               RenderText {#text} at (0,0) size 0x0
           RenderTableRow {TR} at (0,218) size 598x43
             RenderTableCell {TD} at (2,218) size 114x43 [border: (1px inset #808080)] [r=3 c=0 rs=1 cs=1]
-              RenderImage {IMG} at (2,2) size 110x39
+              RenderBlock {IMG} at (2,2) size 110x39
               RenderText {#text} at (0,0) size 0x0
             RenderTableCell {TH} at (118,227) size 478x24 [border: (1px inset #808080)] [r=3 c=1 rs=1 cs=2]
               RenderText {#text} at (208,2) size 62x19
@@ -86,7 +86,7 @@ layer at (0,0) size 785x965
         RenderTableSection {TBODY} at (1,1) size 598x179
           RenderTableRow {TR} at (0,2) size 598x77
             RenderTableCell {TD} at (2,2) size 594x77 [border: (1px inset #808080)] [r=0 c=0 rs=1 cs=3]
-              RenderImage {IMG} at (2,2) size 590x73
+              RenderBlock {IMG} at (2,2) size 590x73
               RenderText {#text} at (0,0) size 0x0
           RenderTableRow {TR} at (0,81) size 598x96
             RenderTableCell {TD} at (2,81) size 111x24 [bgcolor=#94BD73] [border: (1px inset #808080)] [r=1 c=0 rs=1 cs=1]
@@ -134,3 +134,15 @@ layer at (0,0) size 785x965
               RenderBlock {P} at (2,74) size 447x20
                 RenderText {#text} at (0,0) size 68x19
                   text run at (0,0) width 68: "etc., etc. ..."
+layer at (13,13) size 590x73 clip at (14,14) size 588x71
+  RenderBlock {DIV} at (0,0) size 590x73 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (13,190) size 589x33 clip at (14,191) size 587x31
+  RenderBlock {DIV} at (0,0) size 589x33 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (13,229) size 110x39 clip at (14,230) size 108x37
+  RenderBlock {DIV} at (0,0) size 110x39 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16
+layer at (13,591) size 590x73 clip at (14,592) size 588x71
+  RenderBlock {DIV} at (0,0) size 590x73 [border: (1px solid #C0C0C0)]
+    RenderImage {IMG} at (2,2) size 16x16