Remove an extra relayout for non-percent logical height grid items

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 cd2d268e4cc698a6118351e88b355458386dfef6..7197601557c14c85ebd8b51b9611fd2fb12acb3e 100644
--- a/Source/core/rendering/RenderGrid.cpp
+++ b/Source/core/rendering/RenderGrid.cpp
@@ -845,6 +845,14 @@ void RenderGrid::dirtyGrid()
     m_gridIsDirty = true;
 }
 
+static bool gridItemDependsOnGridAreaLogicalHeight(const RenderBox* gridItem)
+{
+    const Length& logicalHeight = gridItem->style()->logicalHeight();
+    // FIXME: This is wrong if the grid area and the grid item have orthogonal writing modes,
+    // but the rest of the code doesn't handle this case anyway (http://crbug.com/234194).
+    return logicalHeight.isPercent();

[ojan, 2013/09/07 17:13:20]

Don't you also need to check maxHeight/minHeight? What about viewport
percentages? You could maybe use RenderBox::hasRelativeLogicalHeight here?

[Julien - ping for review, 2013/09/09 18:04:42]

I think you are right, I will add more testing for that.
AFAICT we are not impacted by viewport percentages.
gridItemDependsOnGridAreaLogicalHeight determines if the grid item's logical
height depends on the grid area's logical height, which is not the case for
viewport percentage.

+}
+
 void RenderGrid::layoutGridItems()
 {
     placeItemsOnGrid();
@@ -870,7 +878,7 @@ void RenderGrid::layoutGridItems()
         LayoutUnit overrideContainingBlockContentLogicalHeight = gridAreaBreadthForChild(child, ForRows, rowTracks);
 
         SubtreeLayoutScope layoutScope(child);
-        if (oldOverrideContainingBlockContentLogicalWidth != overrideContainingBlockContentLogicalWidth || oldOverrideContainingBlockContentLogicalHeight != overrideContainingBlockContentLogicalHeight)
+        if (oldOverrideContainingBlockContentLogicalWidth != overrideContainingBlockContentLogicalWidth || (gridItemDependsOnGridAreaLogicalHeight(child) && oldOverrideContainingBlockContentLogicalHeight != overrideContainingBlockContentLogicalHeight))
             layoutScope.setNeedsLayout(child);
 
         child->setOverrideContainingBlockContentLogicalWidth(overrideContainingBlockContentLogicalWidth);