From ac734805c4cca6bea7e993c6d1a1b7561b59b1a8 Mon Sep 17 00:00:00 2001
From: Matt Woodrow <mwoodrow@mozilla.com>
Date: Thu, 1 Mar 2018 16:53:58 +1300
Subject: [PATCH] Bug 1436510 - Don't attempt partial display list building
 within perspective as we need to build all children to get consistent
 indices. r=miko

---
 layout/generic/nsFrame.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index dc68a903f7c1..b38fcecfca1b 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -2828,6 +2828,16 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
     }
   }
 
+  // nsDisplayPerspective items use an index to keep their PerFrameKey unique.
+  // We need to make sure we build all of them for them to be consistent, so
+  // rebuild all items if we have perspective. Bug 1431249 should remove
+  // this requirement.
+  if (aBuilder->IsRetainingDisplayList() &&
+      ChildrenHavePerspective(disp)) {
+    dirtyRect = visibleRect;
+    aBuilder->MarkFrameModifiedDuringBuilding(this);
+  }
+
   bool inTransform = aBuilder->IsInTransform();
   bool isTransformed = IsTransformed(disp);
   bool hasPerspective = HasPerspective(disp);