[CSS Grid Layout] Fix issues adding new items to grid

Source/core/rendering/RenderGrid.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 173 matching lines @@
     RenderBlock::addChild(newChild, beforeChild);
 
     if (gridIsDirty())
         return;
 
     if (!newChild->isBox()) {
         dirtyGrid();
         return;
     }
 
+    if (style()->gridAutoFlow() != AutoFlowNone) {
+        // The grid needs to be recomputed as it might contain auto-placed items that will change their position.
+        dirtyGrid();
+        return;
+    }
+
     RenderBox* newChildBox = toRenderBox(newChild);
     OwnPtr<GridSpan> rowPositions = resolveGridPositionsFromStyle(newChildBox, ForRows);
     OwnPtr<GridSpan> columnPositions = resolveGridPositionsFromStyle(newChildBox, ForColumns);
     if (!rowPositions || !columnPositions) {
         // The new child requires the auto-placement algorithm to run so we need to recompute the grid fully.
         dirtyGrid();
-    } else {
-        if (gridRowCount() <= rowPositions->finalPositionIndex || gridColumnCount() <= columnPositions->finalPositionIndex) {
-            // FIXME: We could just insert the new child provided we had a primitive to arbitrarily grow the grid.
-            dirtyGrid();
-        } else {
-            insertItemIntoGrid(newChildBox, GridCoordinate(*rowPositions, *columnPositions));
-        }
+        return;

[Julien - ping for review, 2014/03/21 04:10:35]

Not sure what the return brings us here as it really was an else below :-)

     }
+
+    // Grow grid if required.
+    for (size_t i = gridRowCount(); i <= rowPositions->finalPositionIndex; i++)
+        growGrid(ForRows);
+    for (size_t i = gridColumnCount(); i <= columnPositions->finalPositionIndex; i++)
+        growGrid(ForColumns);

[Julien - ping for review, 2014/03/21 04:10:35]

I have been thinking that we need a way to grow the grid more than a single item
at a time. This is for efficiency as well as to support auto-placement with
spanning items.

+
+    insertItemIntoGrid(newChildBox, GridCoordinate(*rowPositions, *columnPositions));
 }
 
 void RenderGrid::removeChild(RenderObject* child)
 {
     RenderBlock::removeChild(child);
 
     if (gridIsDirty())
         return;
 
     ASSERT(child->isBox());
@@ skipping 1164 matching lines @@
     if (isOutOfFlowPositioned())
         return "RenderGrid (positioned)";
     if (isAnonymous())
         return "RenderGrid (generated)";
     if (isRelPositioned())
         return "RenderGrid (relative positioned)";
     return "RenderGrid";
 }
 
 } // namespace WebCore