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

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 827 matching lines @@
     return (flow == AutoFlowColumn) ? ForRows : ForColumns;
 }
 
 void RenderGrid::dirtyGrid()
 {
     m_grid.resize(0);
     m_gridItemCoordinate.clear();
     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();
 
     Vector<GridTrack> columnTracks(gridColumnCount());
     Vector<GridTrack> rowTracks(gridRowCount());
     computedUsedBreadthOfGridTracks(ForColumns, columnTracks, rowTracks);
     ASSERT(tracksAreWiderThanMinTrackBreadth(ForColumns, columnTracks));
     computedUsedBreadthOfGridTracks(ForRows, columnTracks, rowTracks);
     ASSERT(tracksAreWiderThanMinTrackBreadth(ForRows, rowTracks));
 
     for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
         LayoutPoint childPosition = findChildLogicalPosition(child, columnTracks, rowTracks);
 
         // Because the grid area cannot be styled, we don't need to adjust
         // the grid breadth to account for 'box-sizing'.
         LayoutUnit oldOverrideContainingBlockContentLogicalWidth = child->hasOverrideContainingBlockLogicalWidth() ? child->overrideContainingBlockContentLogicalWidth() : LayoutUnit();
         LayoutUnit oldOverrideContainingBlockContentLogicalHeight = child->hasOverrideContainingBlockLogicalHeight() ? child->overrideContainingBlockContentLogicalHeight() : LayoutUnit();
 
         // FIXME: For children in a content sized track, we clear the overrideContainingBlockContentLogicalHeight
         // in minContentForChild / maxContentForChild which means that we will always relayout the child.
         LayoutUnit overrideContainingBlockContentLogicalWidth = gridAreaBreadthForChild(child, ForColumns, columnTracks);
         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);
         child->setOverrideContainingBlockContentLogicalHeight(overrideContainingBlockContentLogicalHeight);
 
         LayoutRect oldChildRect = child->frameRect();
 
         // FIXME: Grid items should stretch to fill their cells. Once we
         // implement grid-{column,row}-align, we can also shrink to fit. For
         // now, just size as if we were a regular child.
@@ skipping 268 matching lines @@
     if (isOutOfFlowPositioned())
         return "RenderGrid (positioned)";
     if (isAnonymous())
         return "RenderGrid (generated)";
     if (isRelPositioned())
         return "RenderGrid (relative positioned)";
     return "RenderGrid";
 }
 
 } // namespace WebCore