Always give RenderParts a RenderLayer.

LayoutTests/platform/linux/svg/zoom/page/zoom-svg-through-object-with-absolute-size-expected.txt

 layer at (0,0) size 800x600
   RenderView at (0,0) size 800x600
 layer at (0,0) size 800x199
   RenderBlock {html} at (0,0) size 800x199.09
     RenderBody {body} at (5.55,5.55) size 788.91x188
       RenderTable {table} at (142.95,0) size 503x188
         RenderTableSection (anonymous) at (0,0) size 503x188
           RenderTableRow {tr} at (0,0) size 503x188
             RenderTableCell {td} at (0,0) size 503x188 [r=0 c=0 rs=1 cs=3]
               RenderTable {table} at (7.44,6) size 490x176
                 RenderTableSection (anonymous) at (0,0) size 490x176
                   RenderTableRow {tr} at (0,1) size 490x66
                     RenderTableCell {td} at (1,1) size 488x65.75 [r=0 c=0 rs=1 cs=2]
                       RenderBlock {h1} at (5.55,19.88) size 478x26
                         RenderText {#text} at (0,0) size 478x25
                           text run at (0,0) width 478: "Both sides should have identical size after zooming"
                   RenderTableRow {tr} at (0,68) size 490x24
                     RenderTableCell {td} at (1,68) size 243x24 [r=1 c=0 rs=1 cs=1]
                       RenderText {#text} at (96,5) size 51x14
                         text run at (96,5) width 51: "SVG Image"
                     RenderTableCell {td} at (245,68) size 244x24 [r=1 c=1 rs=1 cs=1]
                       RenderText {#text} at (95,5) size 54x14
                         text run at (95,5) width 54: "PNG Image"
                   RenderTableRow {tr} at (0,93) size 490x82
                     RenderTableCell {td} at (1,93) size 243x82 [r=2 c=0 rs=1 cs=1]
-                      RenderEmbeddedObject {object} at (99.13,5) size 138.88x69.44
-                        layer at (0,0) size 139x69
-                          RenderView at (0,0) size 139x69
-                        layer at (0,0) size 139x69
-                          RenderSVGRoot {svg} at (23,0) size 93x69
-                            RenderSVGContainer {g} at (28,8) size 73x46
-                              RenderSVGRect {rect} at (29,8) size 10x17 [stroke={[type=SOLID] [color=#000000]}] [x=30.00] [y=46.00] [width=50.00] [height=80.00]
-                              RenderSVGRect {rect} at (48,8) size 10x17 [fill={[type=SOLID] [color=#FF0000]}] [x=130.00] [y=46.00] [width=50.00] [height=80.00]
-                              RenderSVGRect {rect} at (71,8) size 11x17 [stroke={[type=SOLID] [color=#000000]}] [x=250.00] [y=46.00] [width=50.00] [height=80.00]
-                              RenderSVGRect {rect} at (90,8) size 11x17 [fill={[type=SOLID] [color=#FF0000]}] [x=350.00] [y=46.00] [width=50.00] [height=80.00]
-                              RenderSVGRect {rect} at (28,36) size 12x18 [stroke={[type=SOLID] [color=#0000FF] [stroke width=8.00]}] [x=30.00] [y=196.00] [width=50.00] [height=80.00]
-                              RenderSVGRect {rect} at (47,36) size 12x18 [stroke={[type=SOLID] [color=#0000FF] [stroke width=8.00]}] [fill={[type=SOLID] [color=#00FF00]}] [x=130.00] [y=196.00] [width=50.00] [height=80.00]
-                              RenderSVGRect {rect} at (70,36) size 12x18 [stroke={[type=SOLID] [color=#0000FF] [stroke width=8.00]}] [x=250.00] [y=196.00] [width=50.00] [height=80.00]
-                              RenderSVGRect {rect} at (90,37) size 11x16 [fill={[type=SOLID] [color=#00FF00]}] [x=350.00] [y=196.00] [width=50.00] [height=80.00]
-                            RenderSVGText {text} at (10,298) size 272x53 contains 1 chunk(s)
-                              RenderSVGInlineText {#text} at (0,0) size 272x53
-                                chunk 1 text run 1 at (10.00,340.00) startOffset 0 endOffset 16 width 271.30: "$Revision: 1.7 $"
-                            RenderSVGRect {rect} at (23,0) size 93x69 [stroke={[type=SOLID] [color=#000000]}] [x=1.00] [y=1.00] [width=478.00] [height=358.00]
                       RenderText {#text} at (0,0) size 0x0
                     RenderTableCell {td} at (245,93) size 244x82 [r=2 c=1 rs=1 cs=1]
                       RenderImage {img} at (5,5) size 138.88x69.44
                       RenderText {#text} at (0,0) size 0x0
+layer at (256,110) size 139x69
+  RenderEmbeddedObject {object} at (99.13,5) size 138.88x69.44
+    layer at (0,0) size 139x69
+      RenderView at (0,0) size 139x69
+    layer at (0,0) size 139x69
+      RenderSVGRoot {svg} at (23,0) size 93x69
+        RenderSVGContainer {g} at (28,8) size 73x46
+          RenderSVGRect {rect} at (29,8) size 10x17 [stroke={[type=SOLID] [color=#000000]}] [x=30.00] [y=46.00] [width=50.00] [height=80.00]
+          RenderSVGRect {rect} at (48,8) size 10x17 [fill={[type=SOLID] [color=#FF0000]}] [x=130.00] [y=46.00] [width=50.00] [height=80.00]
+          RenderSVGRect {rect} at (71,8) size 11x17 [stroke={[type=SOLID] [color=#000000]}] [x=250.00] [y=46.00] [width=50.00] [height=80.00]
+          RenderSVGRect {rect} at (90,8) size 11x17 [fill={[type=SOLID] [color=#FF0000]}] [x=350.00] [y=46.00] [width=50.00] [height=80.00]
+          RenderSVGRect {rect} at (28,36) size 12x18 [stroke={[type=SOLID] [color=#0000FF] [stroke width=8.00]}] [x=30.00] [y=196.00] [width=50.00] [height=80.00]
+          RenderSVGRect {rect} at (47,36) size 12x18 [stroke={[type=SOLID] [color=#0000FF] [stroke width=8.00]}] [fill={[type=SOLID] [color=#00FF00]}] [x=130.00] [y=196.00] [width=50.00] [height=80.00]
+          RenderSVGRect {rect} at (70,36) size 12x18 [stroke={[type=SOLID] [color=#0000FF] [stroke width=8.00]}] [x=250.00] [y=196.00] [width=50.00] [height=80.00]
+          RenderSVGRect {rect} at (90,37) size 11x16 [fill={[type=SOLID] [color=#00FF00]}] [x=350.00] [y=196.00] [width=50.00] [height=80.00]
+        RenderSVGText {text} at (10,298) size 272x53 contains 1 chunk(s)
+          RenderSVGInlineText {#text} at (0,0) size 272x53
+            chunk 1 text run 1 at (10.00,340.00) startOffset 0 endOffset 16 width 271.30: "$Revision: 1.7 $"
+        RenderSVGRect {rect} at (23,0) size 93x69 [stroke={[type=SOLID] [color=#000000]}] [x=1.00] [y=1.00] [width=478.00] [height=358.00]