Bug 1538736 - Make extra sure Compositables don't refer back to layers after reassignment. r=sotaro

Differential Revision: https://phabricator.services.mozilla.com/D27930

--HG--
extra : moz-landing-system : lando

gfx/layers/composite/CanvasLayerComposite.cpp

@@ -40,9 +40,13 @@ CanvasLayerComposite::~CanvasLayerComposite() {
 
 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;
   }

gfx/layers/composite/ImageLayerComposite.cpp

@@ -47,9 +47,14 @@ ImageLayerComposite::~ImageLayerComposite() {
 
 bool ImageLayerComposite::SetCompositableHost(CompositableHost* aHost) {
   switch (aHost->GetType()) {
-    case CompositableType::IMAGE:
-      mImageHost = static_cast<ImageHost*>(aHost);
+    case CompositableType::IMAGE: {
+      ImageHost* newImageHost = static_cast<ImageHost*>(aHost);
+      if (mImageHost && newImageHost != mImageHost) {
+        mImageHost->Detach(this);
+      }
+      mImageHost = newImageHost;
       return true;
+    }
     default:
       return false;
   }

gfx/layers/composite/PaintedLayerComposite.cpp

@@ -47,9 +47,14 @@ bool 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;
   }

gfx/layers/mlgpu/PaintedLayerMLGPU.cpp

@@ -65,12 +65,16 @@ bool PaintedLayerMLGPU::SetCompositableHost(CompositableHost* aHost) {
   switch (aHost->GetType()) {
     case CompositableType::CONTENT_TILED:
     case CompositableType::CONTENT_SINGLE:
-    case CompositableType::CONTENT_DOUBLE:
+    case CompositableType::CONTENT_DOUBLE: {
+      if (mHost && mHost != aHost->AsContentHost()) {
+        mHost->Detach(this);
+      }
       mHost = aHost->AsContentHost();
       if (!mHost) {
         gfxWarning() << "ContentHostBase is not a ContentHostTexture";
       }
       return true;
+    }
     default:
       return false;
   }