Incorrect use of 'this' keyword in drag/drop file handler

[alexjlockwood]

See this line:

 fileReader.onabort = function(e) {
   this.setState_(State.NONE);
   alert('File read cancelled');
 };

Calling this.setState_ won't work because you are using the function keyword instead of an arrow function.

Just wanted to point this out in case you ever copy/paste this code into a different project.