[CSS Grid Layout] Clear stretched height when conditions don't allow it.

Source/core/layout/LayoutGrid.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 1551 matching lines @@
     // compute margins in order to determine the available height before stretching.
     if (childMarginLogicalHeight == 0)
         childMarginLogicalHeight = computeMarginLogicalHeightForChild(child);
 
     return gridAreaBreadthForChild - childMarginLogicalHeight;
 }
 
 // FIXME: This logic is shared by LayoutFlexibleBox, so it should be moved to LayoutBox.
 void LayoutGrid::applyStretchAlignmentToChildIfNeeded(LayoutBox& child, LayoutUnit gridAreaBreadthForChild)
 {
-    if (ComputedStyle::resolveAlignment(styleRef(), child.styleRef(), ItemPositionStretch) != ItemPositionStretch)
+    if (!allowedToStretchLogicalHeightForChild(child) || ComputedStyle::resolveAlignment(styleRef(), child.styleRef(), ItemPositionStretch) != ItemPositionStretch) {
+        if (child.hasOverrideLogicalContentHeight())

[Julien - ping for review, 2015/06/03 21:33:13]

I would just call clearOverrideLogicalContentHeight() directly. This avoids a
branch (and back in the days when this involved a hash lookup also a lookup).

[jfernandez, 2015/06/05 00:05:30]

Done.

+            child.clearOverrideLogicalContentHeight();

[Julien - ping for review, 2015/06/03 21:33:13]

Thinking out loud here, we should probably think about some design pattern to
avoid that. I have been beaten by similar bugs and I am sure there are more
lurking.

[jfernandez, 2015/06/05 00:05:30]

Yes, I've got the same feeling. I'll add t my TODO list and try to find a more
conscious approach to handle overrideLogicalContentHeight logic.

         return;
+    }
 
     bool hasOrthogonalWritingMode = child.isHorizontalWritingMode() != isHorizontalWritingMode();
-    if (allowedToStretchLogicalHeightForChild(child)) {
-        // FIXME: If the child has orthogonal flow, then it already has an override height set, so use it.
-        // FIXME: grid track sizing and positioning do not support orthogonal modes yet.
-        if (!hasOrthogonalWritingMode) {
-            LayoutUnit stretchedLogicalHeight = availableAlignmentSpaceForChildBeforeStretching(gridAreaBreadthForChild, child);
-            LayoutUnit desiredLogicalHeight = child.constrainLogicalHeightByMinMax(stretchedLogicalHeight, -1);
+    // FIXME: If the child has orthogonal flow, then it already has an override height set, so use it.
+    // FIXME: grid track sizing and positioning do not support orthogonal modes yet.
+    if (!hasOrthogonalWritingMode) {
+        LayoutUnit stretchedLogicalHeight = availableAlignmentSpaceForChildBeforeStretching(gridAreaBreadthForChild, child);
+        LayoutUnit desiredLogicalHeight = child.constrainLogicalHeightByMinMax(stretchedLogicalHeight, -1);
 
-            // FIXME: Can avoid laying out here in some cases. See https://webkit.org/b/87905.
-            bool childNeedsRelayout = desiredLogicalHeight != child.logicalHeight();
-            if (childNeedsRelayout || !child.hasOverrideLogicalContentHeight())
-                child.setOverrideLogicalContentHeight(desiredLogicalHeight - child.borderAndPaddingLogicalHeight());
-            if (childNeedsRelayout) {
-                child.setLogicalHeight(0);
-                child.setNeedsLayout(LayoutInvalidationReason::GridChanged);
-            }
+        // FIXME: Can avoid laying out here in some cases. See https://webkit.org/b/87905.
+        bool childNeedsRelayout = desiredLogicalHeight != child.logicalHeight();
+        if (childNeedsRelayout || !child.hasOverrideLogicalContentHeight())
+            child.setOverrideLogicalContentHeight(desiredLogicalHeight - child.borderAndPaddingLogicalHeight());
+        if (childNeedsRelayout) {
+            child.setLogicalHeight(0);
+            child.setNeedsLayout(LayoutInvalidationReason::GridChanged);
         }
     }
 }
 
 LayoutUnit LayoutGrid::rowPositionForChild(const LayoutBox& child) const
 {
     bool hasOrthogonalWritingMode = child.isHorizontalWritingMode() != isHorizontalWritingMode();
     switch (ComputedStyle::resolveAlignment(styleRef(), child.styleRef(), ItemPositionStretch)) {
     case ItemPositionSelfStart:
         // If orthogonal writing-modes, this computes to 'start'.
@@ skipping 232 matching lines @@
 
     return LayoutPoint(columnPosition, rowPositionForChild(child));
 }
 
 void LayoutGrid::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     GridPainter(*this).paintChildren(paintInfo, paintOffset);
 }
 
 } // namespace blink