Implement CanvasProvider that provides reusable canvas elements.

src/util/CanvasProvider.js

@@ -0,0 +1,16 @@
+CanvasProvider = {
+	canvases: [],
+	getCanvas: function(width, height) {
+		var canvas = this.canvases.length
+			? this.canvases.pop()
+			: document.createElement('canvas');
+		var cleared;
+		canvas.width = width;
+		canvas.height = height;
+		return canvas;
+	},
+
+	returnCanvas: function(canvas) {
+		this.canvases.push(canvas);
+	}
+};