Make Async.

Runtime/painting/image_stream.cs

         }
 
         void _decodeNextFrameAndSchedule() {
-            this._codec.getNextFrame().Then(frame => {
-                    this._nextFrame = frame;
+            var frame = this._codec.getNextFrame();
+            this._nextFrame = frame;
-                    if (this._codec.frameCount == 1) {
-                        this._emitFrame(new ImageInfo(image: this._nextFrame.image, scale: this._scale));
-                        return;
-                    }
+            if (this._codec.frameCount == 1) {
+                this._emitFrame(new ImageInfo(image: this._nextFrame.image, scale: this._scale));
+                return;
+            }
-                    SchedulerBinding.instance.scheduleFrameCallback(this._handleAppFrame);
-                },
-                ex => {
-                    this.reportError(
-                        context: "resolving an image frame",
-                        exception: ex,
-                        informationCollector: this._informationCollector,
-                        silent: true
-                    );
-                });
+            SchedulerBinding.instance.scheduleFrameCallback(this._handleAppFrame);
         }
 
         void _emitFrame(ImageInfo imageInfo) {

Runtime/ui/painting/codec.cs

     public interface Codec : IDisposable {
         int frameCount { get; }
         int repetitionCount { get; }
-        IPromise<FrameInfo> getNextFrame();
+        FrameInfo getNextFrame();
     }
 
     public class ImageCodec : Codec {
             get { return 0; }
         }
 
-        public IPromise<FrameInfo> getNextFrame() {
+        public FrameInfo getNextFrame() {
-            return Promise<FrameInfo>.Resolved(new FrameInfo {
+            return new FrameInfo {
-            });
+            };
         }
 
         public void Dispose() {

Runtime/ui/painting/codec_gif.cs

             }
         }
 
-        public IPromise<FrameInfo> getNextFrame() {
+        public FrameInfo getNextFrame() {
             this._nextFrame();
             this._texture.LoadRawTextureData(this._frameData.gifFrame.bytes);
             this._texture.Apply();
             };
-            return Promise<FrameInfo>.Resolved(this._frameData.frameInfo);
+            return this._frameData.frameInfo;
         }
 
         public void Dispose() {