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

1 files changed, 5 insertions, 1 deletions

diff --git a/gfx/layers/composite/CanvasLayerComposite.cpp b/gfx/layers/composite/CanvasLayerComposite.cpp
index 3c8299e05..86f25b1ee 100644
--- a/gfx/layers/composite/CanvasLayerComposite.cpp
+++ b/gfx/layers/composite/CanvasLayerComposite.cpp
@@ -43,9 +43,13 @@ bool
 CanvasLayerComposite::SetCompositableHost(CompositableHost* aHost)
 {
   switch (aHost->GetType()) {
-    case CompositableType::IMAGE:
+    case CompositableType::IMAGE: {
+      if (mCompositableHost && aHost != mCompositableHost) {
+        mCompositableHost->Detach(this);
+      }
       mCompositableHost = aHost;
       return true;
+    }
     default:
       return false;
   }