Add field trial to extend prerender expiration to 5 minutes.

chrome/browser/prerender/prerender_manager_unittest.cc

Index: chrome/browser/prerender/prerender_manager_unittest.cc
diff --git a/chrome/browser/prerender/prerender_manager_unittest.cc b/chrome/browser/prerender/prerender_manager_unittest.cc
index 6aac8e5d32a7278c8afa017d657b8610e455bc77..d60aaa003c6e1c07d867f4564f6354498b2074eb 100644
--- a/chrome/browser/prerender/prerender_manager_unittest.cc
+++ b/chrome/browser/prerender/prerender_manager_unittest.cc
@@ -292,8 +292,8 @@ TEST_F(PrerenderManagerTest, ExpireTest) {
   EXPECT_TRUE(prerender_manager()->AddSimplePrerender(url));
   EXPECT_EQ(null, prerender_manager()->next_prerender_contents());
   EXPECT_TRUE(prerender_contents->has_started());
-  prerender_manager()->AdvanceTime(prerender_manager()->config().max_age
-                                   + base::TimeDelta::FromSeconds(1));
+  prerender_manager()->AdvanceTime(prerender_manager()->GetMaxAge() +
+                                   base::TimeDelta::FromSeconds(1));
   ASSERT_EQ(null, prerender_manager()->GetEntry(url));
 }