Migrate core/mutator.js to goog.module
Migrate core/mutator.js to goog.module

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