Do not recursively delete prerenders from within deleting prerenders.

chrome/browser/prerender/prerender_unittest.cc

 // Copyright (c) 2012 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 "base/command_line.h"
 #include "base/format_macros.h"
 #include "base/memory/scoped_vector.h"
 #include "base/message_loop.h"
 #include "base/stringprintf.h"
 #include "base/time.h"
@@ skipping 1337 matching lines @@
   EXPECT_EQ(null, prerender_manager()->FindEntry(second_url));
 
   EXPECT_EQ(prerender_contents,
             prerender_manager()->FindAndUseEntry(first_url));
 
   EXPECT_EQ(null, prerender_manager()->FindEntry(first_url));
   EXPECT_EQ(null, prerender_manager()->FindEntry(second_url));
   EXPECT_TRUE(IsEmptyPrerenderLinkManager());
 }
 
+// Creates two prerenders, one of which should start when the first one expires.
+TEST_F(PrerenderTest, LinkManagerExpireRevealingLaunch) {
+  SetConcurrency(1);
+  ASSERT_LT(prerender_manager()->config().max_wait_to_launch,
+            prerender_manager()->config().time_to_live);
+
+  GURL first_url("http://www.willexpire.com");
+  DummyPrerenderContents* first_prerender_contents =
+      prerender_manager()->CreateNextPrerenderContents(
+          first_url, FINAL_STATUS_TIMED_OUT);
+  EXPECT_TRUE(AddSimplePrerender(first_url));
+  EXPECT_EQ(first_prerender_contents,
+            prerender_manager()->FindEntry(first_url));
+
+  // Insert the second prerender so it will be still be launchable when the
+  // first expires.
+  const TimeDelta wait_to_launch_second_prerender =
+      prerender_manager()->config().time_to_live -
+      prerender_manager()->config().max_wait_to_launch +
+      TimeDelta::FromSeconds(2);
+  const TimeDelta wait_for_first_prerender_to_expire =
+      prerender_manager()->config().max_wait_to_launch -
+      TimeDelta::FromSeconds(1);

[mmenke, 2013/01/01 18:18:36]

optional:  This may be a little clearer if you use
wait_for_first_prerender_to_expire to calculate
wait_to_launch_second_prerender...Or not.

[gavinp, 2013/01/02 14:54:04]

Done. Writing these types of equations is always tricky; I think more important
than the definition being right is the TESTS on these values below. I'm
upgrading them to ASSERTs, since it feels weird to EXPECT something static.

+  EXPECT_LT(prerender_manager()->config().time_to_live,
+            wait_to_launch_second_prerender +
+            wait_for_first_prerender_to_expire);
+  EXPECT_GT(prerender_manager()->config().max_wait_to_launch.InSeconds(),
+            wait_for_first_prerender_to_expire.InSeconds());;

[mmenke, 2013/01/01 18:18:36]

nit:  extra semi-colon.

[gavinp, 2013/01/02 14:54:04]

Done.

+
+  prerender_manager()->AdvanceTimeTicks(wait_to_launch_second_prerender);
+  GURL second_url("http://www.willlaunch.com");
+  DummyPrerenderContents* second_prerender_contents =
+      prerender_manager()->CreateNextPrerenderContents(
+          second_url, FINAL_STATUS_USED);
+  EXPECT_FALSE(AddSimplePrerender(second_url));
+
+  // The first prerender is still running, but the second has not yet launched.
+  EXPECT_EQ(first_prerender_contents,
+            prerender_manager()->FindEntry(first_url));
+  PrerenderContents* null = NULL;
+  EXPECT_EQ(null, prerender_manager()->FindEntry(second_url));
+
+  // The first prerender should have died, giving life to the second one.
+  prerender_manager()->AdvanceTimeTicks(wait_for_first_prerender_to_expire);
+  EXPECT_EQ(null, prerender_manager()->FindEntry(first_url));
+  EXPECT_EQ(second_prerender_contents,
+            prerender_manager()->FindAndUseEntry(second_url));
+}
+
 }  // namespace prerender