add drawParagraph

Runtime/ui/painting/canvas.cs

 using System;
+using Unity.UIWidgets.foundation;
 
 namespace Unity.UIWidgets.ui {
     public interface Canvas {
 
         void drawTextBlob(TextBlob textBlob, Offset offset, Paint paint);
 
+        void drawParagraph(Paragraph paragraph, Offset offset);
         void flush();
 
         void reset();
                 offset = offset,
                 paint = new Paint(paint),
             });
+        }
+        
+        public void drawParagraph(Paragraph paragraph, Offset offset) {
+            D.assert(paragraph != null);
+            D.assert(PaintingUtils._offsetIsValid(offset));
+            paragraph.paint(this, offset);
         }
 
         public virtual void flush() {

Tests/Editor/CanvasAndLayers.cs

                 this.clipRRect,
                 this.saveLayer,
                 this.drawLine,
+                this.drawParagraph,
             };
             this._optionStrings = this._options.Select(x => x.Method.Name).ToArray();
             this._selected = 0;
             editorCanvas.flush();
         }
 
+        void drawParagraph() {
+            var pb = new ParagraphBuilder(new ParagraphStyle{});
+            pb.addText("Hello drawParagraph");
+            var paragraph = pb.build();
+            paragraph.layout(new ParagraphConstraints(width:300));
+            var canvas = new CommandBufferCanvas(this._renderTexture, Window.instance.devicePixelRatio,
+                this._meshPool);
+            canvas.drawParagraph(paragraph, new Offset(10f, 100f));
+            canvas.flush();
+        }
+        
         void drawImageRect() {
             if (this._stream == null || this._stream.completer == null || this._stream.completer.currentImage == null) {
                 return;