Remove RenderViewHost parameter from WebContentsObserver::Did{Start|Stop}Loading.

chrome/browser/prerender/prerender_tab_helper.cc

Index: chrome/browser/prerender/prerender_tab_helper.cc
diff --git a/chrome/browser/prerender/prerender_tab_helper.cc b/chrome/browser/prerender/prerender_tab_helper.cc
index 33017f7ae829ff44b799c1483c4a91dbd49eb38d..1d51f925fcf89e872a040724cfd692d764406884 100644
--- a/chrome/browser/prerender/prerender_tab_helper.cc
+++ b/chrome/browser/prerender/prerender_tab_helper.cc
@@ -100,8 +100,7 @@ void PrerenderTabHelper::DidCommitProvisionalLoadForFrame(
                                          web_contents());
 }
 
-void PrerenderTabHelper::DidStopLoading(
-    content::RenderViewHost* render_view_host) {
+void PrerenderTabHelper::DidStopLoading() {
   // Compute the PPLT metric and report it in a histogram, if needed. If the
   // page is still prerendering, record the not swapped in page load time
   // instead.