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..622be2e3b95271e288180d6bac83fa3c7c6f0374 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()
@@ -713,6 +715,16 @@ void RenderView::OnNavigate(const ViewMsg_Navigate_Params& params) {
   if (!webview())
     return;
 
+  LOG(ERROR) << "OnNavigate."
+             << " rv=" << this
+             << " url=" << params.url.spec()
+             << " history_list_offset_=" << history_list_offset_
+             << " history_list_length_=" << history_list_length_
+             << " params.current_history_list_offset="
+             << params.current_history_list_offset
+             << " params.current_history_list_length="
+             << params.current_history_list_length;
+
   bool is_reload =
       params.navigation_type == ViewMsg_Navigate_Type::RELOAD ||
       params.navigation_type == ViewMsg_Navigate_Type::RELOAD_IGNORING_CACHE;
@@ -845,14 +857,21 @@ bool RenderView::IsBackForwardToStaleEntry(
 
   // Check for whether the forward history has been cropped due to a recent
   // navigation the browser didn't know about.
-  if (params.pending_history_list_offset >= history_list_length_)
+  if (params.pending_history_list_offset >= history_list_length_) {
+    LOG(ERROR) << "History Length is cropped."
+               << " rv=" << this
+               << " pending=" << params.pending_history_list_offset
+               << " stored=" << history_list_length_;
     return true;
+  }
 
   // Check for whether this entry has been replaced with a new one.
   int expected_page_id =
       history_page_ids_[params.pending_history_list_offset];
-  if (expected_page_id > 0 && params.page_id != expected_page_id)
+  if (expected_page_id > 0 && params.page_id != expected_page_id) {
+    LOG(ERROR) << "Mismatched page id";
     return true;
+  }
 
   return false;
 }
@@ -1017,6 +1036,22 @@ void RenderView::OnScrollFocusedEditableNodeIntoView() {
   }
 }
 
+void RenderView::OnOffsetAndPruneHistory(int offset) {
+  LOG(ERROR) << "OnOffsetAndPruneHistory."
+             << " offset=" << offset;
+  int current_page_id = -1;
+  if (history_list_offset_ >= 0) {
+    current_page_id = history_page_ids_[history_list_offset_];
+  }
+
+  // We may have multiple things in the list? Or just one?
+  history_list_offset_ = offset;
+  history_list_length_ = offset + 1;
+  if (history_list_length_ >= 0)
+    history_page_ids_.resize(history_list_length_, -1);
+  history_page_ids_[history_list_offset_] = current_page_id;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 // Tell the embedding application that the URL of the active page has changed
@@ -1230,6 +1265,9 @@ void RenderView::UpdateSessionHistory(WebFrame* frame) {
   if (item.isNull())
     return;
 
+  LOG(ERROR) << "Updating session history."
+             << " rv=" << this
+             << " page_id_=" << page_id_;
   Send(new ViewHostMsg_UpdateState(
       routing_id_, page_id_, webkit_glue::HistoryItemToString(item)));
 }
@@ -2493,6 +2531,10 @@ void RenderView::didCommitProvisionalLoad(WebFrame* frame,
     if (history_list_offset_ >= content::kMaxSessionHistoryEntries)
       history_list_offset_ = content::kMaxSessionHistoryEntries - 1;
     history_list_length_ = history_list_offset_ + 1;
+    LOG(ERROR) << "didCommitProvisionalLoad."
+               << " rv=" << this
+               << " page_id_" << page_id_
+               << " history_list_length_=" << history_list_length_;
     history_page_ids_.resize(history_list_length_, -1);
     history_page_ids_[history_list_offset_] = page_id_;
   } else {