Our minifier (tools/jsmin.py) shortens variable names it comes across.
It generally tries to avoid name conflicts caused by renamed variables,
but cannot handle lambda function syntax.

This is what happens here. Both lambda function parameters 'x' and 'y'
are not recognized as identifiers by the minifier and it thus potentially
causes naming conflicts.

BUG=v8:5505

Review-Url: https://codereview.chromium.org/2412533002
Cr-Commit-Position: refs/heads/master@{#40198}