From 33bc0dac7fe6041b24d065354f94bbe4523f336b Mon Sep 17 00:00:00 2001
From: Cameron Kaiser <classilla@floodgap.com>
Date: Sun, 17 Dec 2017 20:59:41 -0800
Subject: [PATCH] #399: abspos edge case M1379306

---
 layout/generic/nsAbsoluteContainingBlock.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/layout/generic/nsAbsoluteContainingBlock.cpp b/layout/generic/nsAbsoluteContainingBlock.cpp
index 7c9d54d94..5350669b7 100644
--- a/layout/generic/nsAbsoluteContainingBlock.cpp
+++ b/layout/generic/nsAbsoluteContainingBlock.cpp
@@ -415,8 +415,10 @@ nsAbsoluteContainingBlock::ReflowAbsoluteFrame(nsIFrame*                aDelegat
 
   // Get the border values
   WritingMode outerWM = aReflowState.GetWritingMode();
-  const LogicalMargin border(outerWM,
-                             aReflowState.mStyleBorder->GetComputedBorder());
+  const LogicalMargin border(outerWM, aDelegatingFrame->GetUsedBorder());
+  // see https://hg.mozilla.org/mozilla-central/file/fe69c6a1b4a3/layout/generic/nsAbsoluteContainingBlock.cpp
+  // for various backbugs XXX
+
   const LogicalMargin margin =
     kidReflowState.ComputedLogicalMargin().ConvertTo(outerWM, wm);
   bool constrainBSize = (aReflowState.AvailableBSize() != NS_UNCONSTRAINEDSIZE)