Move the SVG container code from rendering/svg to layout/svg.

LayoutTests/platform/win/svg/carto.net/textbox-expected.txt

 layer at (0,0) size 800x600
   RenderView at (0,0) size 800x600
 layer at (0,0) size 800x600
   RenderSVGRoot {svg} at (0,0) size 800x600
     LayoutSVGRect {rect} at (0,0) size 800x600 [fill={[type=SOLID] [color=#FFFFFF]}] [x=-1000.00] [y=-1000.00] [width=3000.00] [height=3000.00]
     LayoutSVGContainer {g} at (77,77) size 158x26
       LayoutSVGContainer {g} at (77,77) size 158x26
         LayoutSVGRect {rect} at (77,77) size 158x26 [stroke={[type=SOLID] [color=#696969] [stroke width=1.50]}] [fill={[type=SOLID] [color=#FFFFFF]}] [x=100.00] [y=100.00] [width=200.00] [height=30.00]
-        RenderSVGViewportContainer {svg} at (77,84) size 2x14
+        LayoutSVGViewportContainer {svg} at (77,84) size 2x14
           LayoutSVGContainer {g} at (77,84) size 2x14
             LayoutSVGText {text}
             LayoutSVGPath {line} at (77,84) size 2x14 [stroke={[type=SOLID] [color=#FF0000] [stroke width=1.50]}] [fill={[type=SOLID] [color=#000000]}] [x1=100.00] [y1=125.00] [x2=100.00] [y2=108.50]
     LayoutSVGContainer {g} at (77,22) size 49x26
       LayoutSVGContainer {g} at (77,22) size 49x26
         LayoutSVGRect {rect} at (77,22) size 49x26 [stroke={[type=SOLID] [color=#696969] [stroke width=1.50]}] [fill={[type=SOLID] [color=#FFFFFF]}] [x=100.00] [y=30.00] [width=60.00] [height=30.00]
-        RenderSVGViewportContainer {svg} at (77,28) size 20x16
+        LayoutSVGViewportContainer {svg} at (77,28) size 20x16
           LayoutSVGContainer {g} at (77,28) size 20x16
             LayoutSVGText {text} at (105,36) size 18x20 contains 1 chunk(s)
               LayoutSVGInlineText {#text} at (0,0) size 18x20
                 chunk 1 text run 1 at (105.00,52.00) startOffset 0 endOffset 2 width 17.92: "50"
             LayoutSVGPath {line} at (77,30) size 2x13 [stroke={[type=SOLID] [color=#FF0000] [stroke width=1.50]}] [fill={[type=SOLID] [color=#000000]}] [x1=100.00] [y1=55.00] [x2=100.00] [y2=38.50]
     LayoutSVGContainer {g} at (77,233) size 346x26 [transform={m=((1.00,0.00)(0.00,1.00)) t=(100.00,300.00)}]
       LayoutSVGContainer {g} at (77,233) size 346x26
         LayoutSVGRect {rect} at (77,233) size 182x26 [stroke={[type=SOLID] [color=#696969] [stroke width=1.50]}] [fill={[type=SOLID] [color=#FFFFFF]}] [x=0.00] [y=0.00] [width=230.00] [height=30.00]
-        RenderSVGViewportContainer {svg} at (77,239) size 346x16
+        LayoutSVGViewportContainer {svg} at (77,239) size 346x16
           LayoutSVGContainer {g} at (77,239) size 346x16
             LayoutSVGText {text} at (5,6) size 436x20 contains 1 chunk(s)
               LayoutSVGInlineText {#text} at (0,0) size 436x20
                 chunk 1 text run 1 at (5.00,22.00) startOffset 0 endOffset 66 width 435.20: "This is a transformed textbox with a very, very, very long content"
             LayoutSVGPath {line} at (77,241) size 2x13 [stroke={[type=SOLID] [color=#FF0000] [stroke width=1.50]}] [fill={[type=SOLID] [color=#000000]}] [x1=0.00] [y1=25.00] [x2=0.00] [y2=8.50]
     LayoutSVGContainer {g} at (78,27) size 663x259
       LayoutSVGText {text} at (100,214) size 68x20 contains 1 chunk(s)
         LayoutSVGInlineText {#text} at (0,0) size 68x20
           chunk 1 text run 1 at (100.00,230.00) startOffset 0 endOffset 10 width 67.84: "ResultText"
       LayoutSVGText {text} at (170,34) size 319x20 contains 1 chunk(s)
@@ skipping 10 matching lines @@
             chunk 1 text run 1 at (350.00,338.00) startOffset 0 endOffset 38 width 229.12: "and accepts all characters (up to 300)"
       LayoutSVGText {text} at (620,299) size 299x20 contains 1 chunk(s)
         LayoutSVGInlineText {#text} at (0,0) size 299x20
           chunk 1 text run 1 at (620.00,315.00) startOffset 0 endOffset 51 width 298.24: "Click on this text to reset content of textbox nr 3"
       LayoutSVGText {text} at (620,322) size 328x20 contains 1 chunk(s)
         LayoutSVGInlineText {#text} at (0,0) size 328x20
           chunk 1 text run 1 at (620.00,338.00) startOffset 0 endOffset 54 width 327.68: "Click on this text to randomly reposition textbox nr 3"
       LayoutSVGText {text} at (620,345) size 301x20 contains 1 chunk(s)
         LayoutSVGInlineText {#text} at (0,0) size 301x20
           chunk 1 text run 1 at (620.00,361.00) startOffset 0 endOffset 50 width 300.80: "Click on this text to randomly resize textbox nr 3"