I thought about potentially adding the identifer ref to the error but
that would require allocating a new string or at the very least
increasing the size of the resulting cons string. Given that the
parser is pretty performance sensitive, I've decided to not display
the identifier.

Previously, the error was:
  _test.js:3: Error
  a[foo].c = () => { throw Error(); };
                     ^
  Error
    at a.(anonymous function).c (_test.js:3:26)
    at _test.js:5:1

With this patch, the error becomes:
  _test.js:3: Error
  a[foo].c = () => { throw Error(); };
                     ^
  Error
    at a.<computed>.c (_test.js:3:26)
    at _test.js:5:1

Bug: v8:8823
Change-Id: I557b3517e317652c447ca06c5a400e9625353d9b
Reviewed-on: https://chromium-review.googlesource.com/c/1495017
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59985}