Fix scaling issues that involves width/height (fabricjs#4491)

* fixed
* added a small test
* typo

src/mixins/object_geometry.mixin.js

@@ -453,7 +453,8 @@
         prefix = this.group.transformMatrixKey(skipGroup) + sep;
       };
       return prefix + this.top + sep + this.left + sep + this.scaleX + sep + this.scaleY +
-        sep + this.skewX + sep + this.skewY + sep + this.angle + sep + this.flipX + sep + this.flipY;
+        sep + this.skewX + sep + this.skewY + sep + this.angle + sep + this.flipX + sep + this.flipY +
+        sep + this.width + sep + this.height;
     },
 
     /**

test/unit/object_geometry.js

@@ -331,6 +331,23 @@
     assert.ok(cObj.isOnScreen(), 'zooming out the object is again on screen');
   });
 
+  QUnit.test('transformMatrixKey depends from properties', function(assert) {
+    var cObj = new fabric.Object(
+      { left: -10, top: -10, width: 30, height: 40, strokeWidth: 0});
+    var key1 = cObj.transformMatrixKey();
+    cObj.left = 5;
+    var key2 = cObj.transformMatrixKey();
+    cObj.left = -10;
+    var key3 = cObj.transformMatrixKey();
+    cObj.width = 5;
+    var key4 = cObj.transformMatrixKey();
+    assert.notEqual(key1, key2, 'keys are different');
+    assert.equal(key1, key3, 'keys are equal');
+    assert.notEqual(key4, key2, 'keys are different');
+    assert.notEqual(key4, key1, 'keys are different');
+    assert.notEqual(key4, key3, 'keys are different');
+  });
+
   QUnit.test('isOnScreen with object that include canvas', function(assert) {
     var cObj = new fabric.Object(
       { left: -10, top: -10, width: canvas.getWidth() + 100, height: canvas.getHeight(), strokeWidth: 0});