Support for non-DOM canvases/contexts (backed by bitaps).

samples/openglui/src/gl.dart

Index: samples/openglui/src/gl.dart
===================================================================
--- samples/openglui/src/gl.dart	(revision 18200)
+++ samples/openglui/src/gl.dart	(working copy)
@@ -13,8 +13,28 @@
 export 'dart:html' show WebGLRenderingContext;
 export 'dart:html' show Float32Array;
 export 'dart:html' show ImageElement;
+export 'dart:html' show CanvasElement;
 
-WebGLRenderingContext gl;
-
 log(message) => window.console.log(message);
 
+getDisplayCanvas(resize) {
+  final canvas = new CanvasElement(width: window.innerWidth, height: window.innerHeight);
+  document.body.nodes.add(canvas);
+
+  window.onResize.listen((e) {
+    canvas.width = window.innerWidth;
+    canvas.height = window.innerHeight;
+    resize(canvas.width, canvas.height);
+  });
+  return canvas;
+}
+
+animate(draw) {
+  var render;
+  render = (n) {
+    draw();
+    window.requestAnimationFrame(render);
+  };
+  render(0);
+}
+