Remove usage of deprecated V8 API from pepper.

R=jochen@chromium.org
BUG=324225

Review URL: https://codereview.chromium.org/94993003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237781 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237781