Until now, String.prototype.{trimLeft,trimRight} were non-standard
language extensions, required for Web compatibility.

The proposal at https://github.com/tc39/proposal-string-left-right-trim
standardizes this functionality as String.prototype.{trimStart,trimEnd},
and defines String.prototype.{trimLeft,trimRight} as aliases for
backwards compatibility.

This patch implements that proposal behind the --harmony-string-trimming
flag.

Bug: v8:6530
Change-Id: Id21e624c12a79e6b782efb049a48901b9da7db71
Reviewed-on: https://chromium-review.googlesource.com/867044
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50717}

The changes are (excluding presubmit.py) mechanical. I added the following
lines after the check and iterated the presubmit script until all errors
went away:

f = open(name, "w");
if contents.endswith('\n\n'):
  f.write(contents[0:-1])
else:
  f.write(contents + '\n')

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/82803005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18017 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/18068003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15370 ce2b1a6d-e550-0410-aec6-3dcde31c8c00