From fab9c3f0fac90c45e043c6462b4f0196f548c00c Mon Sep 17 00:00:00 2001
From: Timothy Nikkel <tnikkel@gmail.com>
Date: Sun, 1 Nov 2015 11:45:40 -0600
Subject: [PATCH] Bug 1220020. Recompute the current animated geometry root
 when a child scroll frame forces us to be layerized, and therefore turns us
 into an animated geometry root. r=mstange

---
 layout/generic/nsGfxScrollFrame.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/layout/generic/nsGfxScrollFrame.cpp b/layout/generic/nsGfxScrollFrame.cpp
index d99bf58daef..845b2c30195 100644
--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -3092,7 +3092,14 @@ ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
       //
       // This is not compatible when using containes for root scrollframes.
       MOZ_ASSERT(couldBuildLayer && mScrolledFrame->GetContent());
+      bool needToRecomputeAGR = false;
+      if (!mWillBuildScrollableLayer) {
+        needToRecomputeAGR = true;
+      }
       mWillBuildScrollableLayer = true;
+      if (needToRecomputeAGR) {
+        aBuilder->RecomputeCurrentAnimatedGeometryRoot();
+      }
     }
   }