This removes --harmony-completion, --harmony-concat-spreadable, and
--harmony-tolength and moves the appropriate tests from harmony/ to es6/.
Review URL: https://codereview.chromium.org/1667453002
Cr-Commit-Position: refs/heads/master@{#33712}
--harmony_sloppy includes behavior to turn on sloppy mode lexical
bindings. Before this patch, it also included a way to parse let
which is likely web-incompatible (let is disallowed as an
identifier). This patch splits off the let parsing from the more
general block scoping code, so that block scoping can be developed
independently.
R=adamk
LOG=N
BUG=v8:3305
Review URL: https://codereview.chromium.org/1255013002
Cr-Commit-Position: refs/heads/master@{#29855}
