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

chrome/browser/prerender/prerender_browsertest.cc

Index: chrome/browser/prerender/prerender_browsertest.cc
diff --git a/chrome/browser/prerender/prerender_browsertest.cc b/chrome/browser/prerender/prerender_browsertest.cc
index 9eec60fa294f02a3d36490018784ad8e1cc5b9c2..565ca4eddb408dd1b0d544fdf5e203ea2dbaf2fd 100644
--- a/chrome/browser/prerender/prerender_browsertest.cc
+++ b/chrome/browser/prerender/prerender_browsertest.cc
@@ -3094,10 +3094,19 @@ IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderFavicon) {
   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");
@@ -3117,6 +3126,28 @@ IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderUnload) {
   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) {