e an Image that represents the current contents of the surface.
 This needs to be able to outlive the surface itself (if need be), and
 must faithfully represent the current contents, even if the surface
 is changed after this called (e.g. it is drawn to via its canvas).
 <p>
 If a subset is specified, the impl must make a copy, rather than try to wait
 on copy-on-write.</div>
<dl class="notes">
<dt>Specified by:</dt>
<dd><code><a href="../sketch/Surface.html#onNewImageSnapshot(icyllis.arc3d.core.Rect2ic)">