[CSS Grid Layout] Add support for named grid areas

Source/core/rendering/RenderGrid.cpp

Index: Source/core/rendering/RenderGrid.cpp
diff --git a/Source/core/rendering/RenderGrid.cpp b/Source/core/rendering/RenderGrid.cpp
index 3a9e0a728995d5f6299b9e17e1de1a1cefc964eb..2fd00bdcd12d9b54421c9495005d1808fee93748 100644
--- a/Source/core/rendering/RenderGrid.cpp
+++ b/Source/core/rendering/RenderGrid.cpp
@@ -975,7 +975,6 @@ size_t RenderGrid::resolveNamedGridLinePositionFromStyle(const GridPosition& pos
 
 size_t RenderGrid::resolveGridPositionFromStyle(const GridPosition& position, GridPositionSide side) const
 {
-    // FIXME: Handle other values for grid-{row,column} like ranges or line names.
     switch (position.type()) {
     case ExplicitPosition: {
         ASSERT(position.integerPosition());
@@ -997,8 +996,24 @@ size_t RenderGrid::resolveGridPositionFromStyle(const GridPosition& position, Gr
         return adjustGridPositionForSide(endOfTrack - resolvedPosition, side);
     }
     case NamedGridAreaPosition:
-        // FIXME: Support resolving named grid area (crbug.com/258092).
+    {
+        NamedGridAreaMap::const_iterator it = style()->namedGridArea().find(position.namedGridLine());
+        // Unknown grid area should have been computed to 'auto' by now.
+        ASSERT(it != style()->namedGridArea().end());
+        const GridCoordinate& gridAreaCoordinate = it->value;
+        switch (side) {
+        case ColumnStartSide:
+            return gridAreaCoordinate.columns.initialPositionIndex;
+        case ColumnEndSide:
+            return gridAreaCoordinate.columns.finalPositionIndex;
+        case RowStartSide:
+            return gridAreaCoordinate.rows.initialPositionIndex;
+        case RowEndSide:
+            return gridAreaCoordinate.rows.finalPositionIndex;
+        }
+        ASSERT_NOT_REACHED();
         return 0;
+    }
     case AutoPosition:
     case SpanPosition:
         // 'auto' and span depend on the opposite position for resolution (e.g. grid-row: auto / 1 or grid-column: span 3 / "myHeader").