The HTML parser should lazy attach.

LayoutTests/platform/win/fast/multicol/span/span-as-immediate-child-generated-content-expected.txt

Index: LayoutTests/platform/win/fast/multicol/span/span-as-immediate-child-generated-content-expected.txt
diff --git a/LayoutTests/platform/win/fast/multicol/span/span-as-immediate-child-generated-content-expected.txt b/LayoutTests/platform/win/fast/multicol/span/span-as-immediate-child-generated-content-expected.txt
index 0ebc93f4e34d5deda19c0bad07a3c86030798a1d..a03e80da0fc74fd447e82e25411a33cf446110b4 100644
--- a/LayoutTests/platform/win/fast/multicol/span/span-as-immediate-child-generated-content-expected.txt
+++ b/LayoutTests/platform/win/fast/multicol/span/span-as-immediate-child-generated-content-expected.txt
@@ -1,8 +1,8 @@
-layer at (0,0) size 785x2889
+layer at (0,0) size 785x2909
   RenderView at (0,0) size 785x600
-layer at (0,0) size 785x2889
-  RenderBlock {HTML} at (0,0) size 785x2888.88
-    RenderBody {BODY} at (8,16) size 769x2856.88
+layer at (0,0) size 785x2909
+  RenderBlock {HTML} at (0,0) size 785x2908.88
+    RenderBody {BODY} at (8,16) size 769x2876.88
 layer at (8,16) size 760x437
   RenderBlock {DIV} at (0,0) size 760x436.81 [border: (5px solid #800000)]
     RenderBlock (anonymous multi-column span) at (5,25) size 750x66.81
@@ -288,12 +288,16 @@ layer at (13,2227) size 750x136
     RenderBlock (generated) at (0,252) size 367x20 [bgcolor=#FFFF00]
       RenderText at (0,0) size 150x19
         text run at (0,0) width 150: "After Generated Content"
-layer at (8,2384) size 760x489
-  RenderBlock {DIV} at (0,2368.06) size 760x488.81 [border: (5px solid #800000)]
+layer at (8,2384) size 760x509
+  RenderBlock {DIV} at (0,2368.06) size 760x508.81 [border: (5px solid #800000)]
     RenderBlock (anonymous multi-column span) at (5,297) size 750x66.81
       RenderBlock {H2} at (0,19.91) size 750x27 [bgcolor=#EEEEEE]
         RenderText {#text} at (0,0) size 274x26
           text run at (0,0) width 274: "This is a spanning element."
+    RenderBlock (anonymous) at (5,383.81) size 750x20
+      RenderBlock {SPAN} at (0,0) size 750x20
+        RenderText {#text} at (0,0) size 143x19
+          text run at (0,0) width 143: "Nulla varius enim ac mi."
 layer at (13,2389) size 750x292
   RenderBlock (anonymous multi-column) at (5,5) size 750x292
     RenderBlock (generated) at (0,0) size 367x20 [bgcolor=#FFFF00]
@@ -329,17 +333,14 @@ layer at (13,2389) size 750x292
         text run at (0,160) width 360: "Suspendisse hendrerit quam nec felis. Sed varius turpis vitae"
         text run at (0,180) width 350: "pede. Lorem ipsum dolor sit amet, consectetuer adipiscing"
         text run at (0,200) width 21: "elit."
-layer at (13,2748) size 750x120
-  RenderBlock (anonymous multi-column) at (5,363.81) size 750x120
-    RenderBlock (anonymous) at (0,0) size 367x20
-      RenderInline {SPAN} at (0,0) size 337x19
-        RenderText {#text} at (0,0) size 337x19
-          text run at (0,0) width 337: "Lorem ipsum dolor sit amet, consectetuer adipiscing elit."
-    RenderBlock (anonymous) at (0,20) size 367x20
-      RenderBlock {SPAN} at (0,0) size 367x20
-        RenderText {#text} at (0,0) size 143x19
-          text run at (0,0) width 143: "Nulla varius enim ac mi."
-    RenderBlock (anonymous) at (0,40) size 367x180
+layer at (13,2748) size 750x20
+  RenderBlock (anonymous multi-column) at (5,363.81) size 750x20
+    RenderInline {SPAN} at (0,0) size 337x19
+      RenderText {#text} at (0,0) size 337x19
+        text run at (0,0) width 337: "Lorem ipsum dolor sit amet, consectetuer adipiscing elit."
+layer at (13,2788) size 750x100
+  RenderBlock (anonymous multi-column) at (5,403.81) size 750x100
+    RenderBlock (anonymous) at (0,0) size 367x180
       RenderInline {SPAN} at (0,0) size 364x179
         RenderText {#text} at (0,0) size 364x179
           text run at (0,0) width 337: "Curabitur sollicitudin felis quis lectus. Quisque adipiscing"
@@ -352,6 +353,6 @@ layer at (13,2748) size 750x120
           text run at (0,140) width 364: "hendrerit quam nec felis. Sed varius turpis vitae pede. Lorem"
           text run at (0,160) width 293: "ipsum dolor sit amet, consectetuer adipiscing elit."
       RenderText {#text} at (0,0) size 0x0
-    RenderBlock (generated) at (0,220) size 367x20 [bgcolor=#FFFF00]
+    RenderBlock (generated) at (0,180) size 367x20 [bgcolor=#FFFF00]
       RenderText at (0,0) size 150x19
         text run at (0,0) width 150: "After Generated Content"