"parent" in ParentChange should refere to new parent, not target

See the code in QTBUG-10671.

Add

width: parent.width-10; height: parent.height-10

to the two ParentChanged statements
and add

width, height

to the NumberAnimation's "properties" value in the ParentAnimation.
Run the code and note how the size of the blue rect never changes. This is because the
"parent" in the code added refers to the parent of the "target" (or perhaps the parent of the current context), not the new parent as expected.