Use registry to instantiate flyout from trashcan (#4706)
Use registry to instantiate flyout from trashcan (#4706)

* Instantiate flyouts using registry in trashcan

rachel-fenichel/blockly,mark-friedman/blockly,google/blockly,mark-friedman/blockly,rachel-fenichel/blockly,google/blockly,rachel-fenichel/blockly,google/blockly,google/blockly,rachel-fenichel/blockly,rachel-fenichel/blockly,google/blockly,rachel-fenichel/blockly,mark-friedman/blockly,mark-friedman/blockly,rachel-fenichel/blockly,mark-friedman/blockly,google/blockly,mark-friedman/blockly,google/blockly