Fix flakiness resulting from deleting TabContents before the registrar

chrome/browser/prerender/prerender_contents.cc

Index: chrome/browser/prerender/prerender_contents.cc
===================================================================
--- chrome/browser/prerender/prerender_contents.cc	(revision 86172)
+++ chrome/browser/prerender/prerender_contents.cc	(working copy)
@@ -794,6 +794,7 @@
 TabContentsWrapper* PrerenderContents::ReleasePrerenderContents() {
   render_view_host_observer_.reset();
   prerender_contents_->download_tab_helper()->set_delegate(NULL);
+  tab_contents_observer_registrar_.Observe(NULL);

[dominich, 2011/05/23 16:40:31]

Why are you only calling this in the case that we have a prerender_contents_? Is
there any reason not to always call it in the destructor?

[mmenke, 2011/05/23 16:45:36]

When we don't have a prerender_contents_, we aren't observing a TabContents. 
Putting it here makes this always true.  We set the observer right after
creating the prerender_contents_, and we free it right before releasing or
destroying it.

While I could call it in the destructor instead, this function is now called at
the end of the destructor, as of my download cancellation fix.  It seems to make
the most sense here.  Keep all the stop watching code in one place, and call it
when we release the prerender contents, regardless of whether we're going to
destroy it or use it.

   return prerender_contents_.release();
 }