Remove unused selection related methods from WebView that got moved to WebFrame in r169968 now that Chrome uses the new ones.

BUG=304341

Review URL: https://codereview.chromium.org/215703002

git-svn-id: svn://svn.chromium.org/blink/trunk@170272 bbb929c8-8fbe-4397-9dbb-9b2b20218538