[CSS Grid Layout] Support "sparse" in auto-placed items locked to a row/column

LayoutTests/fast/css-grid-layout/resources/grid.css

Index: LayoutTests/fast/css-grid-layout/resources/grid.css
diff --git a/LayoutTests/fast/css-grid-layout/resources/grid.css b/LayoutTests/fast/css-grid-layout/resources/grid.css
index 69becb516d429c4c57c6fb0d511ef1eca4396ffa..ba4a1863b4160d47077af35ab2661249f2b80cb6 100644
--- a/LayoutTests/fast/css-grid-layout/resources/grid.css
+++ b/LayoutTests/fast/css-grid-layout/resources/grid.css
@@ -69,6 +69,12 @@
     grid-row-end: 3;
 }
 
+.thirdRowSecondColumn {
+    background-color: red;
+    grid-column: 2;
+    grid-row: 3;
+}
+
 .firstAutoRowSecondAutoColumn {
     grid-row: 1 / auto;
     grid-column: 2 / auto;
@@ -176,6 +182,32 @@
     grid-row: span 3;
 }
 
+.autoRowFirstColumnSpanning2 {
+    background-color: maroon;
+    grid-column: 1 / span 2;
+    grid-row: auto;
+}
+
+.autoRowSecondColumnSpanning2 {
+    background-color: olive;
+    grid-column: 2 / span 2;
+    grid-row: auto;
+}
+
+.firstRowSpanning2AutoColumn {
+    background-color: maroon;
+    grid-column: auto;
+    grid-row: 1 / span 2;
+    height: 100%;
+}
+
+.secondRowSpanning2AutoColumn {
+    background-color: olive;
+    grid-column: auto;
+    grid-row: 2 / span 2;
+    height: 100%;
+}
+
 /* Grid element flow. */
 .gridAutoFlowColumnSparse {
     grid-auto-flow: column;