Remove deprecated V8 API usage (String::New) in chrome/renderer/extensions.

BUG=324225
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/94983003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237782 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237782