[CSS Grid Layout] Remove stack from grid-auto-flow syntax

LayoutTests/fast/css-grid-layout/grid-item-named-grid-area-resolution.html

Index: LayoutTests/fast/css-grid-layout/grid-item-named-grid-area-resolution.html
diff --git a/LayoutTests/fast/css-grid-layout/grid-item-named-grid-area-resolution.html b/LayoutTests/fast/css-grid-layout/grid-item-named-grid-area-resolution.html
index 09a97390668709c9868b2f9a0a7311af603212c8..305624e960a9df317523176f74cbbe536e51b72d 100644
--- a/LayoutTests/fast/css-grid-layout/grid-item-named-grid-area-resolution.html
+++ b/LayoutTests/fast/css-grid-layout/grid-item-named-grid-area-resolution.html
@@ -4,7 +4,7 @@
 <link href="resources/grid.css" rel="stylesheet">
 <style>
 .grid {
-    grid-template-rows: (before) 50px (middle) 100px (after);
+    grid-template-rows: (before) 50px (middle) 100px (after) 150px;
     grid-template-columns: 40px 80px 160px;
 }
 
@@ -73,10 +73,10 @@
 </div>
 
 <div style="position: relative">
-    <div class="grid gridWithRepeat gridAutoFlowStack">
+    <div class="grid gridWithRepeat">
         <!-- fifth and sixth are invalid named grid areas. -->
-        <div class="sizedToGridArea gridItemSixthArea" data-offset-x="0" data-offset-y="0" data-expected-width="40" data-expected-height="50"></div>
-        <div class="sizedToGridArea gridItemFifthArea" data-offset-x="0" data-offset-y="0" data-expected-width="40" data-expected-height="50"></div>
+        <div class="sizedToGridArea gridItemSixthArea" data-offset-x="0" data-offset-y="150" data-expected-width="40" data-expected-height="150"></div>
+        <div class="sizedToGridArea gridItemFifthArea" data-offset-x="40" data-offset-y="150" data-expected-width="80" data-expected-height="150"></div>
 
         <div class="sizedToGridArea gridItemFourthArea" data-offset-x="0" data-offset-y="50" data-expected-width="120" data-expected-height="100"></div>
         <div class="sizedToGridArea gridItemThirdArea" data-offset-x="120" data-offset-y="0" data-expected-width="160" data-expected-height="150"></div>