Add RenderFrameHostDelegate and plumb it through all the necessary classes.

This is an empty interface for now. I'm doing this separately in preparation for moving plugin creation from RenderView to RenderFrame.

BUG=245126
R=creis@chromium.org

Review URL: https://codereview.chromium.org/103633002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238709 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238709