Added support for one SKObject to belong to another:

- used when ownership is transferred in native code
 - fixed instance where stream was disposed when in use by typeface

binding/Binding/SKManagedStream.cs

@@ -92,7 +92,12 @@ namespace SkiaSharp
 		}
 
 		public SKManagedStream (Stream managedStream, bool disposeManagedStream)
-			: base (SkiaApi.sk_managedstream_new (), true)
+			: this (managedStream, disposeManagedStream, true)
+		{
+		}
+
+		private SKManagedStream (Stream managedStream, bool disposeManagedStream, bool owns)
+			: base (SkiaApi.sk_managedstream_new (), owns)
 		{
 			if (Handle == IntPtr.Zero) {
 				throw new InvalidOperationException ("Unable to create a new SKManagedStream instance.");
@@ -240,7 +245,8 @@ namespace SkiaSharp
 		private static IntPtr CreateNewInternal (IntPtr managedStreamPtr)
 		{
 			var managedStream = AsManagedStream (managedStreamPtr);
-			var newStream = new SKManagedStream (managedStream.stream);
+			var newStream = new SKManagedStream (managedStream.stream, false, false);
+			managedStream.TakeOwnership (newStream);
 			return newStream.Handle;
 		}
 		#if __IOS__

binding/Binding/SKObject.cs

@@ -19,6 +19,7 @@ namespace SkiaSharp
 	{
 		private static readonly Dictionary<IntPtr, WeakReference> instances = new Dictionary<IntPtr, WeakReference>();
 
+		private readonly List<SKObject> ownedObjects = new List<SKObject>();
 		private IntPtr handle;
 
 		[Preserve]
@@ -37,11 +38,7 @@ namespace SkiaSharp
 
 		~SKObject()
 		{
-			var h = handle;
-
 			Dispose(false);
-
-			DeregisterHandle(h, this);
 		}
 
 		protected bool OwnsHandle { get; private set; }
@@ -58,21 +55,23 @@ namespace SkiaSharp
 
 		public void Dispose()
 		{
-			var h = handle;
-
 			Dispose(true);
-
-			if (h != IntPtr.Zero)
-			{
-				DeregisterHandle(h, this);
-				handle = IntPtr.Zero;
-			}
-
 			GC.SuppressFinalize(this);
 		}
 
 		protected virtual void Dispose(bool disposing)
 		{
+			lock (ownedObjects)
+			{
+				foreach (var child in ownedObjects)
+				{
+					child.Dispose();
+				}
+				ownedObjects.Clear();
+			}
+
+			DeregisterHandle(handle, this);
+			handle = IntPtr.Zero;
 		}
 
 		internal static TSkiaObject GetObject<TSkiaObject>(IntPtr handle)
@@ -170,5 +169,14 @@ namespace SkiaSharp
 				}
 			}
 		}
+
+		internal void TakeOwnership(SKObject obj)
+		{
+			lock (ownedObjects)
+			{
+				ownedObjects.Add(obj);
+			}
+			obj.OwnsHandle = false;
+		}
 	}
 }

binding/Binding/SKTypeface.cs

@@ -53,7 +53,9 @@ namespace SkiaSharp
 		{
 			if (stream == null)
 				throw new ArgumentNullException ("stream");
-			return GetObject<SKTypeface> (SkiaApi.sk_typeface_create_from_stream (stream.Handle, index));
+			var typeface = GetObject<SKTypeface> (SkiaApi.sk_typeface_create_from_stream (stream.Handle, index));
+			typeface?.TakeOwnership (stream);
+			return typeface;
 		}
 
 		public int CountGlyphs (string str)