availableLogicalHeightUsing needs to take flexbox stretched heights into account

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 9844c5910ba36e99629c48051ccd898a83dcb5e2..2f0c98f78df8b94055def04cbc67dc3db7bdd15f 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -3081,6 +3081,13 @@ LayoutUnit LayoutBox::availableLogicalHeightUsing(const Length& h, AvailableLogi
         return logicalHeight() - borderAndPaddingLogicalHeight();
     }
 
+    if (isFlexItem()) {
+        LayoutFlexibleBox& flexBox = toLayoutFlexibleBox(*parent());
+        LayoutUnit stretchedHeight = flexBox.childLogicalHeightForPercentageResolution(*this);
+        if (stretchedHeight != LayoutUnit(-1))
+            return stretchedHeight;
+    }
+
     if (h.isPercentOrCalc() && isOutOfFlowPositioned()) {
         // FIXME: This is wrong if the containingBlock has a perpendicular writing mode.
         LayoutUnit availableHeight = containingBlockLogicalHeightForPositioned(containingBlock());