[css-grid] Fix percentage height on grid item's children

third_party/WebKit/Source/core/layout/LayoutBox.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.cpp b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
index 1cbedcad8db3996a92f175d35cad6c5aeda90a76..d15ad51414803d8f649c4ae907e3c9e06f688c36 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -2733,6 +2733,8 @@ LayoutUnit LayoutBox::computePercentageLogicalHeight(const Length& height) const
         availableHeight = stretchedFlexHeight;
     } else if (hasOverrideContainingBlockLogicalHeight()) {
         availableHeight = overrideContainingBlockContentLogicalHeight();
+    } else if (cb->styleRef().logicalHeight().isAuto() && cb->hasOverrideContainingBlockLogicalHeight()) {

[jfernandez, 2016/06/06 15:15:54]

Nit: better using cbstyle ? 

If we are computing the "availableHeight" why we are adding
logicalHeight().isAuto() to the condition ? Shouldn't we just use that condition
to discriminate from the cases below (eg, isFixed ? )

[Manuel Rego, 2016/06/06 15:55:46]

Sure, done.
The problem is that we'd be using the wrong size in that case.
E.g.
  <div style="display: grid; grid: 100px / 200px;">
    <div style="height: 400px;">
       <div style="height: 50%;">child</div>
    </div>
  </div>

For the grid item, overrideContainingBlockLogicalHeight() will be 100px
(the height of the row).
However the item has 400px height, so the 50% of the child should be resolved
against those 400px.
If I remove the logicalHeight().isAuto() we'd be doing this wrong.

[jfernandez, 2016/06/06 16:18:04]

why not moving the new branch after the one checking out whether "isfixed" ?

[Manuel Rego, 2016/06/06 16:39:59]

I can move it but I still need the isAuto() check.
Note that isFixed() doesn't mean that !isAuto(), there're more cases like:
percentage, calc, intrinsic size, etc.

I put it there to keep it close to the one with
hasOverrideContainingBlockLogicalHeight(),
the one for the grid item itself.

[jfernandez, 2016/06/06 17:45:49]

Yeah, there is a case for the percentage cases below. I don't know, I don't have
a strong opinion, so I think what you thing fits better int he code style of
that method is fine to me. It was that new code looked like a special case and
those branches are dealing with
specific length types of the containing block. I thought that the 'auto' case
was just
another one.

+        availableHeight = cb->overrideContainingBlockContentLogicalHeight();
     } else if (cbstyle.logicalHeight().isFixed()) {
         LayoutUnit contentBoxHeight = cb->adjustContentBoxLogicalHeightForBoxSizing(cbstyle.logicalHeight().value());
         availableHeight = cb->constrainContentBoxLogicalHeightByMinMax(