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

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index 63da47dd6c38ae0151e61c9aaa53724cb3e6ac3a..3f53d355aa467164c1627ee27aa9b8814b4ef69e 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -2708,8 +2708,8 @@ LayoutUnit RenderBox::computePercentageLogicalHeight(const Length& height) const
         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();
 
@@ -2861,10 +2861,10 @@ LayoutUnit RenderBox::computeReplacedLogicalHeightUsing(Length logicalHeight) co
         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