Super calls on computed properties crash the compiler

[ochafik]

Offending code:

class Foo {
  ['m']() { return 1; }
}
class Bar extends Foo {
  ['m']() {
    return super['m']() + 1;
  }
}
console.log(new Bar()['m']());

Produces the following error with --language_in=ES6 --language_out=ES5 -O SIMPLE:

java.lang.RuntimeException: INTERNAL COMPILER ERROR.
Please report this problem.

null
  Node(SUPER): /usr/local/google/home/ochafik/super.js:19:11
    return super['M']() + 1;
  Parent(GETELEM): /usr/local/google/home/ochafik/super.js:19:11
    return super['M']() + 1;

    at com.google.javascript.jscomp.Es6ConvertSuper.visitSuper(Es6ConvertSuper.java:135)
    at com.google.javascript.jscomp.Es6ConvertSuper.visit(Es6ConvertSuper.java:70)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:609)

Note that the following compiles fine since #1125:

class Foo {
  m() { return 1; }
}
class Bar extends Foo {
  m() {
    return super.m() + 1;
  }
}
console.log(new Bar().m());

(happens with output from DDC, where we sometimes use Symbols in conjunction with computed props).