Additional fixes for prerender/instant + browsing history.

content/browser/tab_contents/tab_contents.cc

Index: content/browser/tab_contents/tab_contents.cc
diff --git a/content/browser/tab_contents/tab_contents.cc b/content/browser/tab_contents/tab_contents.cc
index 0b06b975200dce0dce4aec261d136bed54ff41aa..bfdaa8a1ec699dc35450bbb1a08cc6ab4988e8b2 100644
--- a/content/browser/tab_contents/tab_contents.cc
+++ b/content/browser/tab_contents/tab_contents.cc
@@ -596,12 +596,21 @@ bool TabContents::NavigateToEntry(
   return true;
 }
 
-void TabContents::SetHistoryLengthAndClear(int history_length) {
+void TabContents::SetHistoryLengthAndClear(const SiteInstance* site_instance,
+                                           int history_length,
+                                           int32 page_id) {
   RenderViewHost* rvh = render_view_host();
   if (!rvh)
     return;
+  // It's possible that the current render view host is different from the
+  // one that needs to be pruned.

[Charlie Reis, 2011/08/11 20:49:24]

Well, we're hoping it isn't possible if called correctly, but we want to be
safe.  Let's rephrase to something like "Ensure that we update the history of
the intended RenderView."

+  if (rvh->site_instance() != site_instance) {
+    LOG(ERROR) << "Mismatches site instance";
+    return;
+  }
   rvh->Send(new ViewMsg_SetHistoryLengthAndClear(rvh->routing_id(),
-                                                 history_length));
+                                                 history_length,
+                                                 page_id));
 }
 
 void TabContents::Stop() {