Avoid requiring a recalc to update compositing state for iframes

LayoutTests/platform/mac/fast/frames/onlyCommentInIFrame-expected.txt

Index: LayoutTests/platform/mac/fast/frames/onlyCommentInIFrame-expected.txt
diff --git a/LayoutTests/platform/mac/fast/frames/onlyCommentInIFrame-expected.txt b/LayoutTests/platform/mac/fast/frames/onlyCommentInIFrame-expected.txt
index 53c903bcd78d8140fc245bdc43621f5cfb0ccf32..35cd18515f09dab4bb68a30fd18c51af21edbe6f 100644
--- a/LayoutTests/platform/mac/fast/frames/onlyCommentInIFrame-expected.txt
+++ b/LayoutTests/platform/mac/fast/frames/onlyCommentInIFrame-expected.txt
@@ -8,30 +8,32 @@ layer at (0,0) size 800x600
         text run at (0,18) width 773: "construct RenderViews for such iframes. We need to propery construct an empty frame instead, so the RenderView should"
         text run at (0,36) width 502: "have a RenderBlock and RenderBody below it in the dump of the RenderTree. "
       RenderBR {BR} at (502,50) size 0x0
-      RenderPartObject {IFRAME} at (0,54) size 788x14 [border: (2px inset #EEEEEE)]
-        layer at (0,0) size 784x10
-          RenderView at (0,0) size 784x10
-        layer at (0,0) size 784x10
-          RenderBlock {HTML} at (0,0) size 784x10
-            RenderBody {BODY} at (8,8) size 768x0
       RenderText {#text} at (0,0) size 0x0
       RenderBR {BR} at (0,0) size 0x0
       RenderBR {BR} at (0,68) size 0x18
-      RenderPartObject {IFRAME} at (0,86) size 788x14 [border: (2px inset #EEEEEE)]
-        layer at (0,0) size 769x169
-          RenderView at (0,0) size 769x10
-        layer at (0,0) size 769x169
-          RenderBlock {html} at (0,0) size 769x168.88
-            RenderBody {body} at (8,16) size 753x136.88
-              RenderBlock {parsererror} at (16,0) size 721x136.88 [bgcolor=#FFDDDD] [border: (2px solid #CC7777)]
-                RenderBlock {h3} at (18,20.72) size 685x22
-                  RenderText {#text} at (0,0) size 309x22
-                    text run at (0,0) width 309: "This page contains the following errors:"
-                RenderBlock {div} at (18,61.44) size 685x14
-                  RenderText {#text} at (0,0) size 490x14
-                    text run at (0,0) width 490: "error on line 1 at column 15: Extra content at the end of the document"
-                    text run at (490,0) width 0: " "
-                RenderBlock {h3} at (18,94.16) size 685x22
-                  RenderText {#text} at (0,0) size 412x22
-                    text run at (0,0) width 412: "Below is a rendering of the page up to the first error."
       RenderText {#text} at (0,0) size 0x0
+layer at (8,62) size 788x14
+  RenderPartObject {IFRAME} at (0,54) size 788x14 [border: (2px inset #EEEEEE)]
+    layer at (0,0) size 784x10
+      RenderView at (0,0) size 784x10
+    layer at (0,0) size 784x10
+      RenderBlock {HTML} at (0,0) size 784x10
+        RenderBody {BODY} at (8,8) size 768x0
+layer at (8,94) size 788x14
+  RenderPartObject {IFRAME} at (0,86) size 788x14 [border: (2px inset #EEEEEE)]
+    layer at (0,0) size 769x169
+      RenderView at (0,0) size 769x10
+    layer at (0,0) size 769x169
+      RenderBlock {html} at (0,0) size 769x168.88
+        RenderBody {body} at (8,16) size 753x136.88
+          RenderBlock {parsererror} at (16,0) size 721x136.88 [bgcolor=#FFDDDD] [border: (2px solid #CC7777)]
+            RenderBlock {h3} at (18,20.72) size 685x22
+              RenderText {#text} at (0,0) size 309x22
+                text run at (0,0) width 309: "This page contains the following errors:"
+            RenderBlock {div} at (18,61.44) size 685x14
+              RenderText {#text} at (0,0) size 490x14
+                text run at (0,0) width 490: "error on line 1 at column 15: Extra content at the end of the document"
+                text run at (490,0) width 0: " "
+            RenderBlock {h3} at (18,94.16) size 685x22
+              RenderText {#text} at (0,0) size 412x22
+                text run at (0,0) width 412: "Below is a rendering of the page up to the first error."