Handle should_replace_current_entry in prerender.

content/browser/frame_host/navigation_controller_impl.cc

 // Copyright 2013 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/frame_host/navigation_controller_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"  // Temporary
@@ skipping 1211 matching lines @@
 
   FinishRestore(source.last_committed_entry_index_, RESTORE_CURRENT_SESSION);
 
   // Copy the max page id map from the old tab to the new tab.  This ensures
   // that new and existing navigations in the tab's current SiteInstances
   // are identified properly.
   delegate_->CopyMaxPageIDsFrom(source.delegate()->GetWebContents());
 }
 
 void NavigationControllerImpl::CopyStateFromAndPrune(
-    NavigationController* temp) {
+    NavigationController* temp,
+    bool replace_entry) {
   // It is up to callers to check the invariants before calling this.
   CHECK(CanPruneAllButLastCommitted());
 
   NavigationControllerImpl* source =
       static_cast<NavigationControllerImpl*>(temp);
   // 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.  We use a scoped_refptr to ensure the SiteInstance
   // can't be freed during this time period.
   NavigationEntryImpl* last_committed =
       NavigationEntryImpl::FromNavigationEntry(GetLastCommittedEntry());
   scoped_refptr<SiteInstance> site_instance(
       last_committed->site_instance());
   int32 minimum_page_id = last_committed->GetPageID();
   int32 max_page_id =
       delegate_->GetMaxPageIDForSiteInstance(site_instance.get());
 
   // Remove all the entries leaving the active entry.
   PruneAllButLastCommittedInternal();
 
   // We now have one entry, possibly with a new pending entry.  Ensure that
   // adding the entries from source won't put us over the limit.
   DCHECK_EQ(1, GetEntryCount());
-  source->PruneOldestEntryIfFull();
+  if (!replace_entry)
+    source->PruneOldestEntryIfFull();
 
   // Insert the entries from source. Don't use source->GetCurrentEntryIndex as
   // we don't want to copy over the transient entry.  Ignore any pending entry,
   // since it has not committed in source.
   int max_source_index = source->last_committed_entry_index_;
   if (max_source_index == -1)
     max_source_index = source->GetEntryCount();
   else
     max_source_index++;
+
+  // Ignore the source's current entry if merging with replacement.
+  // TODO(davidben): This should preserve entries forward of the current
+  // too. http://crbug.com/317872
+  if (replace_entry && max_source_index > 0)
+    max_source_index--;
+
   InsertEntriesFrom(*source, max_source_index);
 
   // Adjust indices such that the last entry and pending are at the end now.
   last_committed_entry_index_ = GetEntryCount() - 1;
 
   delegate_->SetHistoryLengthAndPrune(site_instance.get(),
                                       max_source_index,
                                       minimum_page_id);
 
   // Copy the max page id map from the old tab to the new tab.  This ensures
@@ skipping 407 matching lines @@
     }
   }
 }
 
 void NavigationControllerImpl::SetGetTimestampCallbackForTest(
     const base::Callback<base::Time()>& get_timestamp_callback) {
   get_timestamp_callback_ = get_timestamp_callback;
 }
 
 }  // namespace content