From 718c1c97fe12f101bcc025e4de4a9f1b0644dfb2 Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@mozilla.com>
Date: Sun, 6 Nov 2016 18:50:15 -0800
Subject: [PATCH] Don't attach shadowable layers if IPDL fails to construct an
 actor. (bug 1314349, r=mattwoodrow)

---
 gfx/layers/ipc/ShadowLayerChild.cpp | 13 ++++++++++---
 gfx/layers/ipc/ShadowLayerChild.h   |  3 ++-
 gfx/layers/ipc/ShadowLayers.cpp     |  9 ++++++++-
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/gfx/layers/ipc/ShadowLayerChild.cpp b/gfx/layers/ipc/ShadowLayerChild.cpp
index b52c229af35e..62d260838f4d 100644
--- a/gfx/layers/ipc/ShadowLayerChild.cpp
+++ b/gfx/layers/ipc/ShadowLayerChild.cpp
@@ -12,20 +12,27 @@
 namespace mozilla {
 namespace layers {
 
-ShadowLayerChild::ShadowLayerChild(ShadowableLayer* aLayer)
-  : mLayer(aLayer)
+ShadowLayerChild::ShadowLayerChild()
+  : mLayer(nullptr)
 { }
 
 ShadowLayerChild::~ShadowLayerChild()
 { }
 
+void
+ShadowLayerChild::SetShadowableLayer(ShadowableLayer* aLayer)
+{
+  MOZ_ASSERT(!mLayer);
+  mLayer = aLayer;
+}
+
 void
 ShadowLayerChild::ActorDestroy(ActorDestroyReason why)
 {
   MOZ_ASSERT(AncestorDeletion != why,
              "shadowable layer should have been cleaned up by now");
 
-  if (AbnormalShutdown == why) {
+  if (AbnormalShutdown == why && mLayer) {
     // This is last-ditch emergency shutdown.  Just have the layer
     // forget its IPDL resources; IPDL-generated code will clean up
     // automatically in this case.
diff --git a/gfx/layers/ipc/ShadowLayerChild.h b/gfx/layers/ipc/ShadowLayerChild.h
index e51813c636dd..38a7f95009c2 100644
--- a/gfx/layers/ipc/ShadowLayerChild.h
+++ b/gfx/layers/ipc/ShadowLayerChild.h
@@ -20,9 +20,10 @@ class ShadowableLayer;
 class ShadowLayerChild : public PLayerChild
 {
 public:
-  explicit ShadowLayerChild(ShadowableLayer* aLayer);
+  ShadowLayerChild();
   virtual ~ShadowLayerChild();
 
+  void SetShadowableLayer(ShadowableLayer* aLayer);
   ShadowableLayer* layer() const { return mLayer; }
 
 protected:
diff --git a/gfx/layers/ipc/ShadowLayers.cpp b/gfx/layers/ipc/ShadowLayers.cpp
index 75986621d0ff..983e3cd875ee 100644
--- a/gfx/layers/ipc/ShadowLayers.cpp
+++ b/gfx/layers/ipc/ShadowLayers.cpp
@@ -749,7 +749,14 @@ ShadowLayerForwarder::ConstructShadowFor(ShadowableLayer* aLayer)
   if (!IPCOpen()) {
     return nullptr;
   }
-  return mShadowManager->SendPLayerConstructor(new ShadowLayerChild(aLayer));
+
+  ShadowLayerChild* child = new ShadowLayerChild();
+  if (!mShadowManager->SendPLayerConstructor(child)) {
+    return nullptr;
+  }
+
+  child->SetShadowableLayer(aLayer);
+  return child;
 }
 
 #if !defined(MOZ_HAVE_PLATFORM_SPECIFIC_LAYER_BUFFERS)