Remove unused WebRemoteFrameImpl::viewImpl() helper.

Added by r182337; an, as it turned out, unused helper that wasn't removed
there.

R=haraken,jochen
BUG=340522

Review URL: https://codereview.chromium.org/606663002

git-svn-id: svn://svn.chromium.org/blink/trunk@182818 bbb929c8-8fbe-4397-9dbb-9b2b20218538