Move GetContextMenuNode from RenderView to RenderFrame.

BUG=304341
R=boliu@chromium.org, nasko@chromium.org, sgurun@chromium.org

Review URL: https://codereview.chromium.org/191293006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256003 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256003