Comments not recorded in delete event

[NeilFraser]

In the playground, turn on event logging and open the console.
Create any block (I'll use 'not' in this example) and place it on the workspace.
Add a 'hello world' comment to this block. Note that a Change event is correctly created.
Delete the block. Note that the Delete event's oldXML.outerHTML lacks the comment:

<block type="logic_negate" id="TDR|)+6F]?Id!;Pl9GcJ" x="137" y="212"></block>

Then if undo is executed, the block reappears without the comment.

This is not a regression.

[rachel-fenichel]

@kchadha FYI

[RoboErikG]

Investigated some. The problem is that BlockSVG.dispose disposes of the icons before super.dispose which is where the delete event gets recorded. Since the icon owns the comment the comment gets destroyed before we can save it.

Short term I'll investigate if we can just destroy the icons after calling super, but long term the icon probably shouldn't own the comment like that.