Use zero height / width for compute canvas (#3369)
Use zero height / width for compute canvas (#3369)

* Make the blockly compute canvas have no height or width

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