Add WasShown/WasHidden to RenderFrameObserver.

content/browser/web_contents/web_contents_impl.h

Index: content/browser/web_contents/web_contents_impl.h
diff --git a/content/browser/web_contents/web_contents_impl.h b/content/browser/web_contents/web_contents_impl.h
index d65036dbbc584e764eb579ff287e16ca5b3aa178..c8a0355b6cb4377934b56cb1b68346e33b35c5e2 100644
--- a/content/browser/web_contents/web_contents_impl.h
+++ b/content/browser/web_contents/web_contents_impl.h
@@ -644,6 +644,7 @@ class CONTENT_EXPORT WebContentsImpl
   FRIEND_TEST_ALL_PREFIXES(FormStructureBrowserTest, HTMLFiles);
   FRIEND_TEST_ALL_PREFIXES(NavigationControllerTest, HistoryNavigate);
   FRIEND_TEST_ALL_PREFIXES(RenderFrameHostManagerTest, PageDoesBackAndReload);
+  FRIEND_TEST_ALL_PREFIXES(SitePerProcessBrowserTest, CrossSiteIframe);
 
   // So InterstitialPageImpl can access SetIsLoading.
   friend class InterstitialPageImpl;
@@ -674,6 +675,10 @@ class CONTENT_EXPORT WebContentsImpl
   // watching |web_contents|. No-op if there is no such observer.
   void RemoveDestructionObserver(WebContentsImpl* web_contents);
 
+  // Traverses all the RenderFrameHosts in the FrameTree and creates a set
+  // all the unique RenderWidgetHosts.
+  std::set<RenderWidgetHostImpl*> GetRenderWidgetHostsInTree();
+
   // Callback function when showing JavaScript dialogs.  Takes in a routing ID
   // pair to identify the RenderFrameHost that opened the dialog, because it's
   // possible for the RenderFrameHost to be deleted by the time this is called.