Paint editor fixes

objects.js

@@ -4519,7 +4519,7 @@ Costume.prototype.bounds = function () {
 
 Costume.prototype.shrinkWrap = function () {
     // adjust my contents'  bounds to my visible bounding box
-    var bb = this.boundingBox(),
+    var bb = this.boundingBox().expandBy(3), // tolerance for anti-aliasing
         ext = bb.extent(),
         pic = newCanvas(ext),
         ctx = pic.getContext('2d');

paint.js

@@ -539,8 +539,8 @@ PaintCanvasMorph.prototype.centermerge = function(a, b) {
     );
 };
 
-PaintCanvasMorph.prototype.clearCanvas = function() {
-    this.fixLayout();
+PaintCanvasMorph.prototype.clearCanvas = function() {
+    this.buildContents();
     this.drawNew();
     this.changed();
 };