# HG changeset patch
# User Kartikaya Gupta <kgupta@mozilla.com>
# Date 1521554487 14400
# Node ID c5277595787694fdbfaab5ccf36da79418f18997
# Parent  f4669f081b150c798622fc4b3afa0f653e166783
Bug 1447157 - Avoid crashing if an unregistered layer tree gets adopted. r=botond

It looks like we can get layer tree adopted messages when the compositor
doesn't have an entry for that layer tree in sIndirectLayerTrees. So we
need to null-check all the things we pull out of that structure - all
the properties are already null-checked except for the mParent. This
patch adds a null check around that as well.

MozReview-Commit-ID: 2fb4SdvgSrG

diff --git a/gfx/layers/ipc/CompositorBridgeParent.cpp b/gfx/layers/ipc/CompositorBridgeParent.cpp
--- a/gfx/layers/ipc/CompositorBridgeParent.cpp
+++ b/gfx/layers/ipc/CompositorBridgeParent.cpp
@@ -1589,20 +1589,22 @@ CompositorBridgeParent::RecvMapAndNotify
 
 mozilla::ipc::IPCResult
 CompositorBridgeParent::RecvAdoptChild(const uint64_t& child)
 {
   RefPtr<APZSampler> oldApzSampler;
   APZCTreeManagerParent* parent;
   {
     MonitorAutoLock lock(*sIndirectLayerTreesLock);
-    // We currently don't support adopting children from one compositor to
-    // another if the two compositors don't have the same options.
-    MOZ_ASSERT(sIndirectLayerTrees[child].mParent->mOptions == mOptions);
-    oldApzSampler = sIndirectLayerTrees[child].mParent->mApzSampler;
+    if (sIndirectLayerTrees[child].mParent) {
+      // We currently don't support adopting children from one compositor to
+      // another if the two compositors don't have the same options.
+      MOZ_ASSERT(sIndirectLayerTrees[child].mParent->mOptions == mOptions);
+      oldApzSampler = sIndirectLayerTrees[child].mParent->mApzSampler;
+    }
     NotifyChildCreated(child);
     if (sIndirectLayerTrees[child].mLayerTree) {
       sIndirectLayerTrees[child].mLayerTree->SetLayerManager(mLayerManager, GetAnimationStorage());
       // Trigger composition to handle a case that mLayerTree was not composited yet
       // by previous CompositorBridgeParent, since nsRefreshDriver might wait composition complete.
       ScheduleComposition();
     }
     if (mWrBridge && sIndirectLayerTrees[child].mWrBridge) {