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

content/renderer/render_view.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/renderer/render_view.h"
 
 #include <algorithm>
 #include <cmath>
 #include <string>
 #include <vector>
@@ skipping 685 matching lines @@
     IPC_MESSAGE_HANDLER(ViewMsg_ContextMenuClosed, OnContextMenuClosed)
     // TODO(viettrungluu): Move to a separate message filter.
 #if defined(ENABLE_FLAPPER_HACKS)
     IPC_MESSAGE_HANDLER(PepperMsg_ConnectTcpACK, OnConnectTcpACK)
 #endif
 #if defined(OS_MACOSX)
     IPC_MESSAGE_HANDLER(ViewMsg_SetInLiveResize, OnSetInLiveResize)
 #endif
     IPC_MESSAGE_HANDLER(ViewMsg_UpdateRemoteAccessClientFirewallTraversal,
                         OnUpdateRemoteAccessClientFirewallTraversal)
+    IPC_MESSAGE_HANDLER(ViewMsg_SetHistoryLengthAndClear,
+                        OnSetHistoryLengthAndClear)
     // Have the super handle all other messages.
     IPC_MESSAGE_UNHANDLED(handled = RenderWidget::OnMessageReceived(message))
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
 void RenderView::OnNavigate(const ViewMsg_Navigate_Params& params) {
   if (!webview())
     return;
 
@@ skipping 294 matching lines @@
 void RenderView::OnScrollFocusedEditableNodeIntoView() {
   WebKit::WebNode node = GetFocusedNode();
   if (!node.isNull()) {
     if (IsEditableNode(node))
       // TODO(varunjain): Change webkit API to scroll a particular node into
       // view and use that API here instead.
       webview()->scrollFocusedNodeIntoView();
   }
 }
 
+void RenderView::OnSetHistoryLengthAndClear(int history_length) {
+  DCHECK(history_length >= 0);
+
+  // history_list_length_ may be 0 if this is called between
+  // a navigate and a commit of the provisional load. Otherwise,
+  // only add one entry, regardless of how long the current history is.

[Charlie Reis, 2011/08/09 22:51:42]

Please add a TODO about investigating what happens if a prerendered page
navigates to several entries before it is swapped in.  Seems like it could cause
issues if we simply cropped those entries from the history, since the page might
assume it could go back to earlier states.

[cbentzel, 2011/08/09 23:14:23]

This does match what the NavigationController does in CopyStateFromAndPrune - it
leaves only the "active entry" - but this may be incorrect behavior. Another
approach is to cancel prerenders if location's or pushState's are attempted. 

Regardless, I added a TODO and will investigate.

+  int new_history_list_length = history_length;
+  if (history_list_length_ > 0) {

[Charlie Reis, 2011/08/09 22:51:42]

Nit: no braces on a one-liner.

[cbentzel, 2011/08/09 23:14:23]

I always mismatch the style guide here [perhaps due to latent disagreement with
the rule].

Done.

+    ++new_history_list_length;
+  }
+
+  // Remember the current page id for the end of the list.
+  int current_page_id = -1;

[Charlie Reis, 2011/08/09 22:51:42]

Is this needed, or is page_id_ sufficient?

[cbentzel, 2011/08/09 23:14:23]

page_id_ does look sufficient. I'm wondering if that should be removed longer
term to prevent redundant data which may drift. 

+  if (history_list_offset_ >= 0)
+    current_page_id = history_page_ids_[history_list_offset_];
+
+  // Generate the new list.
+  std::vector<int32> new_history_page_ids_(new_history_list_length, -1);

[Charlie Reis, 2011/08/09 22:51:42]

Nit: local variable shouldn't have an underscore, should it?

[cbentzel, 2011/08/09 23:14:23]

Done.

+  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
 void RenderView::UpdateURL(WebFrame* frame) {
   WebDataSource* ds = frame->dataSource();
   DCHECK(ds);
 
   const WebURLRequest& request = ds->request();
   const WebURLRequest& original_request = ds->originalRequest();
   const WebURLResponse& response = ds->response();
@@ skipping 3432 matching lines @@
 }
 #endif
 
 void RenderView::OnContextMenuClosed(
     const webkit_glue::CustomContextMenuContext& custom_context) {
   if (custom_context.is_pepper_menu)
     pepper_delegate_.OnContextMenuClosed(custom_context);
   else
     context_menu_node_.reset();
 }