Fix regression with back-button not working on prerendered and instant pages.

content/renderer/render_view.cc

Index: content/renderer/render_view.cc
diff --git a/content/renderer/render_view.cc b/content/renderer/render_view.cc
index 972349f99357ff3f7c6cac7319e352f3c04c2599..7dbcd4b0bafb7c81d5008846fb23ab9c786698fe 100644
--- a/content/renderer/render_view.cc
+++ b/content/renderer/render_view.cc
@@ -703,6 +703,7 @@ bool RenderView::OnMessageReceived(const IPC::Message& message) {
 #endif
     IPC_MESSAGE_HANDLER(ViewMsg_UpdateRemoteAccessClientFirewallTraversal,
                         OnUpdateRemoteAccessClientFirewallTraversal)
+    IPC_MESSAGE_HANDLER(ViewMsg_ShiftHistory, OnShiftHistory)
     // Have the super handle all other messages.
     IPC_MESSAGE_UNHANDLED(handled = RenderWidget::OnMessageReceived(message))
   IPC_END_MESSAGE_MAP()
@@ -1017,6 +1018,21 @@ void RenderView::OnScrollFocusedEditableNodeIntoView() {
   }
 }
 
+void RenderView::OnShiftHistory(int history_length) {
+  DCHECK(history_length >= 0);
+  DCHECK(history_list_length_ == 0 || history_list_length_ == 1);
+  int current_page_id = -1;
+  if (history_list_offset_ >= 0)
+    current_page_id = history_page_ids_[history_list_offset_];
+  int new_history_list_length = history_length + history_list_length_;
+  std::vector<int32> new_history_page_ids_(new_history_list_length, -1);
+  if (current_page_id != -1)
+    new_history_page_ids_[new_history_list_length - 1] = current_page_id;
+  new_history_page_ids_.swap(history_page_ids_);
+  history_list_offset_ = new_history_list_length - 1;
+  history_list_length_ = new_history_list_length;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 // Tell the embedding application that the URL of the active page has changed