Move DisownOpener to RenderFrameHost / RenderFrameProxyHost.

BUG=304341
TEST=RenderFrameHostManagerTest.Disown*

Review URL: https://codereview.chromium.org/505443002

Cr-Commit-Position: refs/heads/master@{#291717}
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 623cbf6..f1a9d02 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -3682,7 +3682,7 @@
   // Notify all swapped out RenderViewHosts for this tab.  This is important
   // in case we go back to them, or if another window in those processes tries
   // to access window.opener.
-  GetRenderManager()->DidDisownOpener(render_frame_host->GetRenderViewHost());
+  GetRenderManager()->DidDisownOpener(render_frame_host);
 }
 
 void WebContentsImpl::DocumentOnLoadCompleted(