From 32dff95bd84c77d24991125df8fa4bf39b6b502b Mon Sep 17 00:00:00 2001
From: Mats Palmgren <mats@mozilla.com>
Date: Fri, 18 May 2018 21:09:21 +0200
Subject: [PATCH] Bug 1458902 - [css-grid] Re-resolve row-gap against the sum
 of row track sizes for auto-sized grid containers.  r=dholbert

Per CSSWG resolution in:
https://github.com/w3c/csswg-drafts/issues/1921#issuecomment-342269371
---
 layout/generic/nsGridContainerFrame.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/layout/generic/nsGridContainerFrame.cpp b/layout/generic/nsGridContainerFrame.cpp
index 92377bee6be0..c6e285ba2ec1 100644
--- a/layout/generic/nsGridContainerFrame.cpp
+++ b/layout/generic/nsGridContainerFrame.cpp
@@ -5990,6 +5990,11 @@ nsGridContainerFrame::Reflow(nsPresContext*           aPresContext,
                           computedISize, bSize);
 
   if (!prevInFlow) {
+    if (computedBSize == NS_AUTOHEIGHT && stylePos->mRowGap.HasPercent()) {
+      // Re-resolve the row-gap now that we know our intrinsic block-size.
+      gridReflowInput.mRows.mGridGap =
+        nsLayoutUtils::ResolveGapToLength(stylePos->mRowGap, bSize);
+    }
     // Apply 'align/justify-content' to the grid.
     // CalculateTrackSizes did the columns.
     gridReflowInput.mRows.AlignJustifyContent(stylePos, wm, contentArea.Size(wm));