Fix issues when PrerenderContents::Destroy() is called during TabContents destruction.

chrome/browser/prerender/prerender_contents.cc

Index: chrome/browser/prerender/prerender_contents.cc
===================================================================
--- chrome/browser/prerender/prerender_contents.cc	(revision 86287)
+++ chrome/browser/prerender/prerender_contents.cc	(working copy)
@@ -137,6 +137,7 @@
       has_stopped_loading_(false),
       final_status_(FINAL_STATUS_MAX),
       prerendering_has_started_(false),
+      prerendering_has_been_cancelled_(false),
       child_id_(-1),
       route_id_(-1) {
   DCHECK(prerender_manager != NULL);
@@ -364,6 +365,9 @@
 
 PrerenderContents::~PrerenderContents() {
   DCHECK(final_status_ != FINAL_STATUS_MAX);
+  DCHECK(prerendering_has_been_cancelled_ ||
+         final_status_ == FINAL_STATUS_USED ||
+         final_status_ == FINAL_STATUS_CONTROL_GROUP);
 
   // If we haven't even started prerendering, we were just in the control
   // group, which means we do not want to record the status.
@@ -710,9 +714,12 @@
 }
 
 void PrerenderContents::Destroy(FinalStatus final_status) {
-  if (prerender_manager_->IsPendingDelete(this))
+  if (prerendering_has_been_cancelled_)
     return;
 
+  prerendering_has_been_cancelled_ = true;
+  prerender_manager_->MoveEntryToPendingDelete(this);

[cbentzel, 2011/05/23 18:51:28]

Is there a reason MoveEntryToPendingDelete moved up here?

[mmenke, 2011/05/23 18:55:36]

Yes, it's just for style - prerender_has_been_cancelled_ is closely associated
with being queued for deletion, so it makes the most sense to me to set
prerender_has_been_cancelled_ at the same time we queue the deletion.  Also
makes sense to set prerender_has_been_cancelled_ to true right after checking if
it's already true.

Of course, the same argument could be made for setting final_status as well.

+
   if (child_id_ != -1 && route_id_ != -1) {
     // Cancel the prerender in the PrerenderTracker.  This is needed
     // because destroy may be called directly from the UI thread without calling
@@ -730,9 +737,8 @@
       NOTREACHED();
     }
   }
+  set_final_status(final_status);
 
-  prerender_manager_->MoveEntryToPendingDelete(this);
-  set_final_status(final_status);
   // We may destroy the PrerenderContents before we have initialized the
   // RenderViewHost. Otherwise set the Observer's PrerenderContents to NULL to
   // avoid any more messages being sent.