[CSS Grid Layout] Support sparse in auto-placement algorithm

LayoutTests/fast/css-grid-layout/grid-item-auto-placement-definite-span.html

Index: LayoutTests/fast/css-grid-layout/grid-item-auto-placement-definite-span.html
diff --git a/LayoutTests/fast/css-grid-layout/grid-item-auto-placement-definite-span.html b/LayoutTests/fast/css-grid-layout/grid-item-auto-placement-definite-span.html
index 35e2ae1e7f537bce030c825628bf92f179ad90c8..3457d4b2b53f64cd3a1eba8cf55c774fd12d3559 100644
--- a/LayoutTests/fast/css-grid-layout/grid-item-auto-placement-definite-span.html
+++ b/LayoutTests/fast/css-grid-layout/grid-item-auto-placement-definite-span.html
@@ -56,6 +56,15 @@
         <div class="sizedToGridArea autoRowFirstColumnSpanning2" data-offset-x="0" data-offset-y="0" data-expected-width="200" data-expected-height="50"></div>
         <div class="sizedToGridArea autoRowSecondColumnSpanning2" data-offset-x="100" data-offset-y="50" data-expected-width="200" data-expected-height="50"></div>
         <div class="sizedToGridArea autoRowFirstColumnSpanning3" data-offset-x="0" data-offset-y="100" data-expected-width="300" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="0" data-offset-y="150" data-expected-width="100" data-expected-height="50"></div>
+    </div>
+</div>
+
+<div style="position: relative">
+    <div class="grid gridAutoFlowRowDense">
+        <div class="sizedToGridArea autoRowFirstColumnSpanning2" data-offset-x="0" data-offset-y="0" data-expected-width="200" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowSecondColumnSpanning2" data-offset-x="100" data-offset-y="50" data-expected-width="200" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowFirstColumnSpanning3" data-offset-x="0" data-offset-y="100" data-expected-width="300" data-expected-height="50"></div>
         <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="200" data-offset-y="0" data-expected-width="100" data-expected-height="50"></div>
         <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="0" data-offset-y="50" data-expected-width="100" data-expected-height="50"></div>
     </div>
@@ -72,10 +81,29 @@
 </div>
 
 <div style="position: relative">
+    <div class="grid gridAutoFlowRowDense">
+        <div class="sizedToGridArea firstRowSpanning2AutoColumn" data-offset-x="0" data-offset-y="0" data-expected-width="100" data-expected-height="100"></div>
+        <div class="sizedToGridArea secondRowSpanning2AutoColumn" data-offset-x="100" data-offset-y="50" data-expected-width="100" data-expected-height="100"></div>
+        <div class="sizedToGridArea firstRowSpanning3AutoColumn" data-offset-x="200" data-offset-y="0" data-expected-width="100" data-expected-height="150"></div>
+        <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="100" data-offset-y="0" data-expected-width="100" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="0" data-offset-y="100" data-expected-width="100" data-expected-height="50"></div>
+    </div>
+</div>
+
+<div style="position: relative">
     <div class="grid gridAutoFlowColumn">

[Julien - ping for review, 2014/07/14 16:22:39]

Ditto.

         <div class="sizedToGridArea firstRowSpanning2AutoColumn" data-offset-x="0" data-offset-y="0" data-expected-width="100" data-expected-height="100"></div>
         <div class="sizedToGridArea secondRowSpanning2AutoColumn" data-offset-x="100" data-offset-y="50" data-expected-width="100" data-expected-height="100"></div>
         <div class="sizedToGridArea firstRowSpanning3AutoColumn" data-offset-x="200" data-offset-y="0" data-expected-width="100" data-expected-height="150"></div>
+        <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="300" data-offset-y="0" data-expected-width="100" data-expected-height="50"></div>
+    </div>
+</div>
+
+<div style="position: relative">
+    <div class="grid gridAutoFlowColumnDense">
+        <div class="sizedToGridArea firstRowSpanning2AutoColumn" data-offset-x="0" data-offset-y="0" data-expected-width="100" data-expected-height="100"></div>
+        <div class="sizedToGridArea secondRowSpanning2AutoColumn" data-offset-x="100" data-offset-y="50" data-expected-width="100" data-expected-height="100"></div>
+        <div class="sizedToGridArea firstRowSpanning3AutoColumn" data-offset-x="200" data-offset-y="0" data-expected-width="100" data-expected-height="150"></div>
         <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="0" data-offset-y="100" data-expected-width="100" data-expected-height="50"></div>
         <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="100" data-offset-y="0" data-expected-width="100" data-expected-height="50"></div>
     </div>
@@ -91,5 +119,15 @@
     </div>
 </div>
 
+<div style="position: relative">
+    <div class="grid gridAutoFlowColumnDense">
+        <div class="sizedToGridArea autoRowFirstColumnSpanning2" data-offset-x="0" data-offset-y="0" data-expected-width="200" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowSecondColumnSpanning2" data-offset-x="100" data-offset-y="50" data-expected-width="200" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowFirstColumnSpanning3" data-offset-x="0" data-offset-y="100" data-expected-width="300" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="0" data-offset-y="50" data-expected-width="100" data-expected-height="50"></div>
+        <div class="sizedToGridArea autoRowAutoColumn" data-offset-x="200" data-offset-y="0" data-expected-width="100" data-expected-height="50"></div>
+    </div>
+</div>
+
 </body>
 </html>