Additional fixes for prerender/instant + browsing history.

content/browser/tab_contents/navigation_controller.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/tab_contents/navigation_controller.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "base/time.h"
@@ skipping 865 matching lines @@
   needs_reload_ = true;
   InsertEntriesFrom(source, source.entry_count());
 
   session_storage_namespace_ = source.session_storage_namespace_->Clone();
 
   FinishRestore(source.last_committed_entry_index_, false);
 }
 
 void NavigationController::CopyStateFromAndPrune(NavigationController* source,
                                                  bool remove_first_entry) {
+  // The SiteInstance and page_id of the last committed entry needs to be
+  // remembered at this point, in case there is only one committed entry
+  // and it is pruned.
+  NavigationEntry* last_committed = GetLastCommittedEntry();
+  SiteInstance* site_instance =
+      last_committed ? last_committed->site_instance() : NULL;
+  int32 minimum_page_id = last_committed ? last_committed->page_id() : -1;
+
   // This code is intended for use when the last entry is the active entry.
   DCHECK((transient_entry_index_ != -1 &&
           transient_entry_index_ == entry_count() - 1) ||
          (pending_entry_ && (pending_entry_index_ == -1 ||
                              pending_entry_index_ == entry_count() - 1)) ||
          (!pending_entry_ && last_committed_entry_index_ == entry_count() - 1));
 
   if (remove_first_entry && entry_count()) {
+    // If there is only one committed entry, then it needs to be erased in the
+    // RenderView, but any newly committed entries will be retained.
+    DCHECK(minimum_page_id >= 0);
+    if (entry_count() == 1)
+      ++minimum_page_id;

[Charlie Reis, 2011/08/13 00:29:04]

Can you add a comment explaining why this is necessary?  I'm not following.

[cbentzel, 2011/08/13 02:19:12]

Done.

     // Save then restore the pending entry (RemoveEntryAtIndexInternal chucks
     // the pending entry).
     NavigationEntry* pending_entry = pending_entry_;
     pending_entry_ = NULL;
     int pending_entry_index = pending_entry_index_;
     RemoveEntryAtIndexInternal(0);
     // Restore the pending entry.
     if (pending_entry_index != -1) {
       pending_entry_index_ = pending_entry_index - 1;
       if (pending_entry_index_ != -1)
@@ skipping 21 matching lines @@
   if (pending_entry_index_ != -1)
     pending_entry_index_ = entry_count() - 1;
   if (transient_entry_index_ != -1) {
     // There's a transient entry. In this case we want the last committed to
     // point to the previous entry.
     transient_entry_index_ = entry_count() - 1;
     if (last_committed_entry_index_ != -1)
       last_committed_entry_index_--;
   }
 
-  // Update the history in the RenderView.
-  tab_contents_->SetHistoryLengthAndClear(max_source_index);
+  tab_contents_->SetHistoryLengthAndPrune(site_instance,
+                                          max_source_index,
+                                          minimum_page_id);
 }
 
 void NavigationController::PruneAllButActive() {
   if (transient_entry_index_ != -1) {
     // There is a transient entry. Prune up to it.
     DCHECK_EQ(entry_count() - 1, transient_entry_index_);
     entries_.erase(entries_.begin(), entries_.begin() + transient_entry_index_);
     transient_entry_index_ = 0;
     last_committed_entry_index_ = -1;
     pending_entry_index_ = -1;
@@ skipping 224 matching lines @@
   size_t insert_index = 0;
   for (int i = 0; i < max_index; i++) {
     // When cloning a tab, copy all entries except interstitial pages
     if (source.entries_[i].get()->page_type() != INTERSTITIAL_PAGE) {
       entries_.insert(entries_.begin() + insert_index++,
                       linked_ptr<NavigationEntry>(
                           new NavigationEntry(*source.entries_[i])));
     }
   }
 }