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);
+  DCHECK(history_list_length_ == 0 || history_list_length_ == 1);

[Charlie Reis, 2011/08/09 20:59:31]

Should we return early if this isn't the case?  Release builds will proceed
without hitting this DCHECK, and it doesn't seem safe to continue if we're not
in this initial state.

[cbentzel, 2011/08/09 21:21:12]

Yes. Changed to returning early.

+  int current_page_id = -1;

[Charlie Reis, 2011/08/09 20:59:31]

I think the page_id_ field should be the same thing, right?  Maybe you can use
that and DCHECK that it's correct.

+  if (history_list_offset_ >= 0)
+    current_page_id = history_page_ids_[history_list_offset_];
+  int new_history_list_length = history_length + history_list_length_;

[Charlie Reis, 2011/08/09 20:59:31]

Why are we adding the two?  It sounds like we're supposed to be setting it to
the given history_length, but this shifts it by the given amount.

More specifically, are there actually separate cases when the
history_list_length_ will be 0 and 1?  I would have guessed it to be 1, and just
set the history_list_length_ to the argument plus 1.

[cbentzel, 2011/08/09 21:21:12]

The prerendered page could be swapped in between the initial navigate and the
commit of the provisional load, when history_list_length_ is 0. I added a
comment for this.

+  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
 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();
 }