Prevent DCHECK (And later double deletion) when

PrerenderContents::Destroy() is called in response to
TabContents destruction.

Re-enables PrerenderBrowserTest.PrerenderHttpAuthentication,
which ran into the issue on ChromeOS.

BUG=82835,82913
TEST=PrerenderBrowserTest.PrerenderHttpAuthentication on ChromeOS

Review URL: http://codereview.chromium.org/7017014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@86339 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/prerender/prerender_browsertest.cc

@@ -89,7 +89,7 @@ class TestPrerenderContents : public PrerenderContents {
         " when testing URL " << prerender_url().path();
     // Prerendering RenderViewHosts should be hidden before the first
     // navigation, so this should be happen for every PrerenderContents for
-    // while a RenderViewHost is created, regardless of whether or not it's
+    // which a RenderViewHost is created, regardless of whether or not it's
     // used.
     if (new_render_view_host_) {
       EXPECT_TRUE(was_hidden_);
@@ -519,9 +519,9 @@ IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderIframeDelayLoadPlugin) {
 // Renders a page that contains a prerender link to a page that contains an
 // iframe with a source that requires http authentication. This should not
 // prerender successfully.
-// Flaky, and crbug.com was down when discovered, so no crbug entry.
+// Flaky:  http://crbug.com/82913.
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest,
-                       DISABLED_PrerenderHttpAuthentication) {
+                       FLAKY_PrerenderHttpAuthentication) {
   PrerenderTestURL("files/prerender/prerender_http_auth_container.html",
                    FINAL_STATUS_AUTH_NEEDED,
                    1);

chrome/browser/prerender/prerender_contents.cc

@@ -137,6 +137,7 @@ PrerenderContents::PrerenderContents(PrerenderManager* prerender_manager,
       has_stopped_loading_(false),
       final_status_(FINAL_STATUS_MAX),
       prerendering_has_started_(false),
+      prerendering_has_been_cancelled_(false),
       child_id_(-1),
       route_id_(-1),
       starting_page_id_(-1) {
@@ -366,6 +367,9 @@ FinalStatus PrerenderContents::final_status() const {
 
 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.
@@ -712,9 +716,12 @@ void PrerenderContents::DidStopLoading() {
 }
 
 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);
+
   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
@@ -732,9 +739,8 @@ void PrerenderContents::Destroy(FinalStatus final_status) {
       NOTREACHED();
     }
   }
-
-  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.

chrome/browser/prerender/prerender_contents.h

@@ -339,6 +339,10 @@ class PrerenderContents : public RenderViewHostDelegate,
 
   bool prerendering_has_started_;
 
+  // Tracks whether or not prerendering has been cancelled by calling Destroy.
+  // Used solely to prevent double deletion.
+  bool prerendering_has_been_cancelled_;
+
   // Time at which we started to load the URL.  This is used to compute
   // the time elapsed from initiating a prerender until the time the
   // (potentially only partially) prerendered page is shown to the user.

chrome/browser/prerender/prerender_manager_unittest.cc

@@ -66,7 +66,7 @@ class TestPrerenderManager : public PrerenderManager {
 
   virtual ~TestPrerenderManager() {
     if (next_prerender_contents()) {
-      next_prerender_contents()->set_final_status(
+      next_prerender_contents_.release()->Destroy(
           FINAL_STATUS_MANAGER_SHUTDOWN);
     }
     // Set the final status for all PrerenderContents with an expected final