Add two tests to ensure WebContents does not leak on prerender swap in

chrome/browser/prerender/prerender_browsertest.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 <stddef.h>
 #include <deque>
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 3076 matching lines @@
   favicon::FaviconDriver* favicon_driver =
       favicon::ContentFaviconDriver::FromWebContents(GetActiveWebContents());
   if (!favicon_driver->FaviconIsValid()) {
     // If the favicon has not been set yet, wait for it to be.
     FaviconUpdateWatcher favicon_update_watcher(GetActiveWebContents());
     favicon_update_watcher.Wait();
   }
   EXPECT_TRUE(favicon_driver->FaviconIsValid());
 }
 
+// Checks that when prerendered page is swapped in and the referring page
+// neither had set an unload nor it had set a beforeunload handler, the old
+// WebContents would not leak.

[mmenke, 2016/05/04 17:54:32]

nit:  would - does or will

[pasko, 2016/05/09 13:34:59]

Done.

+IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderOldWebContentsDeleted) {
+  PrerenderTestURL("/prerender/prerender_page.html", FINAL_STATUS_USED, 1);
+  WebContentsDestructionObserver destruction_observer(GetActiveWebContents());
+  NavigateToDestURL();
+  destruction_observer.Wait();
+}
+
 // Checks that when a prerendered page is swapped in to a referring page, the
 // unload handlers on the referring page are executed and its WebContents is
 // destroyed.
-// TODO(pasko): A similar test for BeforeUnload. See http://crbug.com/600693
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderUnload) {
   // Matches URL in prerender_loader_with_unload.html.
   const GURL unload_url("http://unload-url.test");
   base::FilePath empty_file = ui_test_utils::GetTestFilePath(
       base::FilePath(), base::FilePath(FILE_PATH_LITERAL("empty.html")));
   RequestCounter unload_counter;
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
       base::Bind(&CreateCountingInterceptorOnIO,
                  unload_url, empty_file, unload_counter.AsWeakPtr()));
 
   set_loader_path("/prerender/prerender_loader_with_unload.html");
   PrerenderTestURL("/prerender/prerender_page.html", FINAL_STATUS_USED, 1);
   WebContentsDestructionObserver destruction_observer(GetActiveWebContents());
   NavigateToDestURL();
   unload_counter.WaitForCount(1);
   destruction_observer.Wait();
 }
 
+// Checks that a beforeunload handler is executed on the referring page when a
+// prerendered page is swapped in. Also checks that its WebContents of the

[mmenke, 2016/05/04 17:54:32]

nit: its -> the

[pasko, 2016/05/09 13:34:59]

Done.

+// referring page is destroyed.
+IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderBeforeUnload) {
+  // This URL is requested from prerender_loader_with_beforeunload.html.
+  const GURL beforeunload_url("http://unload-url.test");
+  base::FilePath empty_file = ui_test_utils::GetTestFilePath(
+      base::FilePath(), base::FilePath(FILE_PATH_LITERAL("empty.html")));
+  RequestCounter request_counter;
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(&CreateCountingInterceptorOnIO,
+                 beforeunload_url, empty_file, request_counter.AsWeakPtr()));
+
+  set_loader_path("/prerender/prerender_loader_with_beforeunload.html");
+  PrerenderTestURL("/prerender/prerender_page.html", FINAL_STATUS_USED, 1);
+  WebContentsDestructionObserver destruction_observer(GetActiveWebContents());
+  NavigateToDestURL();
+  request_counter.WaitForCount(1);
+  destruction_observer.Wait();
+}
+
 // Checks that a hanging unload on the referring page of a prerender swap does
 // not crash the browser on exit.
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderHangingUnload) {
   // Matches URL in prerender_loader_with_unload.html.
   const GURL hang_url("http://unload-url.test");
   base::FilePath empty_file = ui_test_utils::GetTestFilePath(
       base::FilePath(), base::FilePath(FILE_PATH_LITERAL("empty.html")));
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
       base::Bind(&CreateHangingFirstRequestInterceptorOnIO,
@@ skipping 956 matching lines @@
 
   NavigateToDestURL();
   EXPECT_EQ(1U, task_manager.tasks().size());
 }
 
 }  // namespace
 
 #endif  // defined(ENABLE_TASK_MANAGER)
 
 }  // namespace prerender