Avoid unnecessary forced layout of flex items when stretching

Source/core/rendering/RenderFlexibleBox.cpp

 /*
  * Copyright (C) 2011 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1026 matching lines @@
 {
     size_t count = 0;
     for (size_t i = 0; i < children.size(); ++i) {
         RenderBox* child = children[i];
         if (!child->isOutOfFlowPositioned())
             ++count;
     }
     return count;
 }
 
-bool RenderFlexibleBox::needToStretchChild(RenderBox* child)
-{
-    if (alignmentForChild(child) != AlignStretch)
-        return false;
-
-    Length crossAxisLength = isHorizontalFlow() ? child->style()->height() : child->style()->width();
-    return crossAxisLength.isAuto();
-}
-
 void RenderFlexibleBox::resetAutoMarginsAndLogicalTopInCrossAxis(RenderBox* child)
 {
     if (hasAutoMarginsInCrossAxis(child))
         child->updateLogicalHeight();
 }
 
 void RenderFlexibleBox::layoutAndPlaceChildren(LayoutUnit& crossAxisOffset, const OrderedFlexItemList& children, const Vector<LayoutUnit>& childSizes, LayoutUnit availableFreeSpace, bool relayoutChildren, Vector<LineContext>& lineContexts)
 {
     ASSERT(childSizes.size() == children.size());
 
@@ skipping 11 matching lines @@
     bool shouldFlipMainAxis = !isColumnFlow() && !isLeftToRightFlow();
     for (size_t i = 0; i < children.size(); ++i) {
         RenderBox* child = children[i];
         if (child->isOutOfFlowPositioned()) {
             prepareChildForPositionedLayout(child, mainAxisOffset, crossAxisOffset, FlipForRowReverse);
             continue;
         }
 
         LayoutUnit childPreferredSize = childSizes[i] + mainAxisBorderAndPaddingExtentForChild(child);
         setLogicalOverrideSize(child, childPreferredSize);
-        // FIXME: Can avoid laying out here in some cases. See https://webkit.org/b/87905.
-        if (needToStretchChild(child) || childPreferredSize != mainAxisExtentForChild(child))
+        if (childPreferredSize != mainAxisExtentForChild(child)) {
             child->setChildNeedsLayout(MarkOnlyThis);
-        else {
+        } else {
             // To avoid double applying margin changes in updateAutoMarginsInCrossAxis, we reset the margins here.
             resetAutoMarginsAndLogicalTopInCrossAxis(child);
         }
         updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, child);
         child->layoutIfNeeded();
 
         updateAutoMarginsInMainAxis(child, autoMarginOffset);
 
         LayoutUnit childCrossAxisMarginBoxExtent;
         if (alignmentForChild(child) == AlignBaseline && !hasAutoMarginsInCrossAxis(child)) {
@@ skipping 265 matching lines @@
             ASSERT(child);
             LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
             LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
             LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
             adjustAlignmentForChild(child, newOffset - originalOffset);
         }
     }
 }
 
 }