Switch BackgroundContents to use TabContents instead of RenderViewHost.

content/browser/tab_contents/tab_contents_observer.cc

Index: content/browser/tab_contents/tab_contents_observer.cc
===================================================================
--- content/browser/tab_contents/tab_contents_observer.cc	(revision 109469)
+++ content/browser/tab_contents/tab_contents_observer.cc	(working copy)
@@ -25,12 +25,12 @@
     NavigationController::ReloadType reload_type) {
 }
 
-void TabContentsObserver::DidNavigateMainFramePostCommit(
+void TabContentsObserver::DidNavigateMainFrame(
     const content::LoadCommittedDetails& details,
     const ViewHostMsg_FrameNavigate_Params& params) {
 }
 
-void TabContentsObserver::DidNavigateAnyFramePostCommit(
+void TabContentsObserver::DidNavigateAnyFrame(
     const content::LoadCommittedDetails& details,
     const ViewHostMsg_FrameNavigate_Params& params) {
 }