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..6f3d7c99c578a8eff9014ce14eeabbfe90f42a6f 100644
--- a/content/renderer/render_view.cc
+++ b/content/renderer/render_view.cc
@@ -703,6 +703,8 @@ bool RenderView::OnMessageReceived(const IPC::Message& message) {
 #endif
     IPC_MESSAGE_HANDLER(ViewMsg_UpdateRemoteAccessClientFirewallTraversal,
                         OnUpdateRemoteAccessClientFirewallTraversal)
+    IPC_MESSAGE_HANDLER(ViewMsg_OffsetAndPruneHistory,
+                        OnOffsetAndPruneHistory)
     // Have the super handle all other messages.
     IPC_MESSAGE_UNHANDLED(handled = RenderWidget::OnMessageReceived(message))
   IPC_END_MESSAGE_MAP()
@@ -1017,6 +1019,22 @@ void RenderView::OnScrollFocusedEditableNodeIntoView() {
   }
 }
 
+void RenderView::OnOffsetAndPruneHistory(int offset) {
+  int current_page_id = -1;
+  if (history_list_offset_ >= 0) {
+    current_page_id = history_page_ids_[history_list_offset_];
+  }
+
+  history_list_offset_ = offset;
+  history_list_length_ = offset + 1;
+  if (history_list_length_ >= 0)
+    history_page_ids_.resize(history_list_length_, -1);
+  // Older entries also need to be invalidated.
+  for (int i = 0; i < history_list_offset_; ++i)
+    history_page_ids_[i] = -1;
+  history_page_ids_[history_list_offset_] = current_page_id;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 // Tell the embedding application that the URL of the active page has changed