Add Group#getBounds().

src/item/Group.js

@@ -17,6 +17,24 @@ Group = Item.extend({
 		}
 	},
 	
+	getBounds: function() {
+		if(this.children.length) {
+			var rect = this.children[0].bounds;
+			var x1 = rect.x;
+			var y1 = rect.y;
+			var x2 = rect.x + rect.width;
+			var y2 = rect.y + rect.height;
+			for(var i = 1, l = this.children.length; i < l; i++) {
+				var rect2 = this.children[i].bounds;
+				x1 = Math.min(rect2.x, x1);
+				y1 = Math.min(rect2.y, y1);
+				x2 = Math.max(rect2.x + rect2.width, x1 + x2 - x1);
+				y2 = Math.max(rect2.y + rect2.height, y1 + y2 - y1);
+			}
+		}
+		return new Rectangle(x1, y1, x2 - x1, y2 - y1);
+	},
+	
 	/**
 	 * Specifies whether the group item is to be clipped.
 	 * When setting to true, the first child in the group is automatically