Reland "Avoid layout/full-repaint on view height change if possible"

Source/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 2690 matching lines @@
     bool skippedAutoHeightContainingBlock = false;
     RenderBlock* cb = containingBlock();
     const RenderBox* containingBlockChild = this;
     LayoutUnit rootMarginBorderPaddingHeight = 0;
     while (!cb->isRenderView() && skipContainingBlockForPercentHeightCalculation(cb)) {
         if (cb->isBody() || cb->isRoot())
             rootMarginBorderPaddingHeight += cb->marginBefore() + cb->marginAfter() + cb->borderAndPaddingLogicalHeight();
         skippedAutoHeightContainingBlock = true;
         containingBlockChild = cb;
         cb = cb->containingBlock();
-        cb->addPercentHeightDescendant(const_cast<RenderBox*>(this));
     }
+    cb->addPercentHeightDescendant(const_cast<RenderBox*>(this));

[Julien - ping for review, 2014/03/11 01:23:37]

Wouldn't this mean that any containing block between the percentage height
descendant and |cb| would return that it has no percentage height descendant
even if it does?

[Xianzhu, 2014/03/11 19:05:13]

I think this depends on how we define "percentage height descendants" of an
object. If we mean it "descendants whose percent height calculation directly
depend on this object's size", I think the behavior is just what we want.

Even the original code didn't mean it "all descendants with percent height",
otherwise the loop should not just stop at
!skipContaingBlockForPercentHeightCalculation(), but needs to loop until it
reaches the root renderer.

How about renaming "percentHeightDescendant" to "percentHeightDependent"?

 
     RenderStyle* cbstyle = cb->style();
 
     // A positioned element that specified both top/bottom or that specifies height should be treated as though it has a height
     // explicitly specified that can be used for any percentage computations.
     bool isOutOfFlowPositionedWithSpecifiedHeight = cb->isOutOfFlowPositioned() && (!cbstyle->logicalHeight().isAuto() || (!cbstyle->logicalTop().isAuto() && !cbstyle->logicalBottom().isAuto()));
 
     bool includeBorderPadding = isTable();
 
     if (isHorizontalWritingMode() != cb->isHorizontalWritingMode())
@@ skipping 131 matching lines @@
 
 LayoutUnit RenderBox::computeReplacedLogicalHeightUsing(Length logicalHeight) const
 {
     switch (logicalHeight.type()) {
         case Fixed:
             return adjustContentBoxLogicalHeightForBoxSizing(logicalHeight.value());
         case Percent:
         case Calculated:
         {
             RenderObject* cb = isOutOfFlowPositioned() ? container() : containingBlock();
-            while (cb->isAnonymous()) {
+            while (cb->isAnonymous())
                 cb = cb->containingBlock();
+            if (cb->isRenderBlock())
                 toRenderBlock(cb)->addPercentHeightDescendant(const_cast<RenderBox*>(this));
-            }
 
             // FIXME: This calculation is not patched for block-flow yet.
             // https://bugs.webkit.org/show_bug.cgi?id=46500
             if (cb->isOutOfFlowPositioned() && cb->style()->height().isAuto() && !(cb->style()->top().isAuto() || cb->style()->bottom().isAuto())) {
                 ASSERT_WITH_SECURITY_IMPLICATION(cb->isRenderBlock());
                 RenderBlock* block = toRenderBlock(cb);
                 LogicalExtentComputedValues computedValues;
                 block->computeLogicalHeight(block->logicalHeight(), 0, computedValues);
                 LayoutUnit newContentHeight = computedValues.m_extent - block->borderAndPaddingLogicalHeight() - block->scrollbarLogicalHeight();
                 LayoutUnit newHeight = block->adjustContentBoxLogicalHeightForBoxSizing(newContentHeight);
@@ skipping 1812 matching lines @@
         return 0;
 
     if (!layoutState && !flowThreadContainingBlock())
         return 0;
 
     RenderBlock* containerBlock = containingBlock();
     return containerBlock->offsetFromLogicalTopOfFirstPage() + logicalTop();
 }
 
 } // namespace WebCore