Make extra sure Compositables don't refer back to layers after reassignment.

1 files changed, 7 insertions, 2 deletions

diff --git a/gfx/layers/composite/PaintedLayerComposite.cpp b/gfx/layers/composite/PaintedLayerComposite.cpp
index b58f5d690..232cc4ef4 100644
--- a/gfx/layers/composite/PaintedLayerComposite.cpp
+++ b/gfx/layers/composite/PaintedLayerComposite.cpp
@@ -49,9 +49,14 @@ PaintedLayerComposite::SetCompositableHost(CompositableHost* aHost)
   switch (aHost->GetType()) {
     case CompositableType::CONTENT_TILED:
     case CompositableType::CONTENT_SINGLE:
-    case CompositableType::CONTENT_DOUBLE:
-      mBuffer = static_cast<ContentHost*>(aHost);
+    case CompositableType::CONTENT_DOUBLE: {
+      ContentHost* newBuffer = static_cast<ContentHost*>(aHost);
+      if (mBuffer && newBuffer != mBuffer) {
+        mBuffer->Detach(this);
+      }
+      mBuffer = newBuffer;
       return true;
+    }
     default:
       return false;
   }