Avoid requiring a recalc to update compositing state for iframes

LayoutTests/platform/mac/svg/hixie/rendering-model/003-expected.txt

Index: LayoutTests/platform/mac/svg/hixie/rendering-model/003-expected.txt
diff --git a/LayoutTests/svg/hixie/rendering-model/003-expected.txt b/LayoutTests/platform/mac/svg/hixie/rendering-model/003-expected.txt
similarity index 55%
copy from LayoutTests/svg/hixie/rendering-model/003-expected.txt
copy to LayoutTests/platform/mac/svg/hixie/rendering-model/003-expected.txt
index 220ef5db973560de667b483d56fc01ea8cbe7dab..7366af5649c7fcc4a5c6c465d2ed8f7b9dab0490 100644
--- a/LayoutTests/svg/hixie/rendering-model/003-expected.txt
+++ b/LayoutTests/platform/mac/svg/hixie/rendering-model/003-expected.txt
@@ -8,9 +8,10 @@ layer at (0,0) size 800x406
           text run at (0,0) width 431: "There should be two identical blue squares below, and no scrollbars."
       RenderBlock {div} at (0,34) size 160x160 [bgcolor=#000080]
       RenderBlock {p} at (0,210) size 784x164
-        RenderPartObject {iframe} at (0,0) size 160x160 [bgcolor=#FF0000]
-          layer at (0,0) size 160x160
-            RenderView at (0,0) size 160x160
-          layer at (0,0) size 160x160
-            RenderSVGRoot {svg} at (0,0) size 160x160
-              RenderSVGRect {rect} at (0,0) size 160x160 [fill={[type=SOLID] [color=#000080]}] [x=0.00] [y=0.00] [width=160.00] [height=160.00]
+layer at (8,226) size 160x160
+  RenderPartObject {iframe} at (0,0) size 160x160 [bgcolor=#FF0000]
+    layer at (0,0) size 160x160
+      RenderView at (0,0) size 160x160
+    layer at (0,0) size 160x160
+      RenderSVGRoot {svg} at (0,0) size 160x160
+        RenderSVGRect {rect} at (0,0) size 160x160 [fill={[type=SOLID] [color=#000080]}] [x=0.00] [y=0.00] [width=160.00] [height=160.00]