Run unload handlers when navigating to about:blank using PlzNavigate.

chrome/browser/extensions/extension_resource_request_policy_apitest.cc

Index: chrome/browser/extensions/extension_resource_request_policy_apitest.cc
diff --git a/chrome/browser/extensions/extension_resource_request_policy_apitest.cc b/chrome/browser/extensions/extension_resource_request_policy_apitest.cc
index 0eb1128a15b0c59234d638e2fe0c795bebc8717d..d3c3fcb9c66bb3551dba1901c2a0ea2eaf4b4b86 100644
--- a/chrome/browser/extensions/extension_resource_request_policy_apitest.cc
+++ b/chrome/browser/extensions/extension_resource_request_policy_apitest.cc
@@ -15,6 +15,7 @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_observer.h"
+#include "content/public/common/browser_side_navigation_policy.h"
 #include "content/public/test/browser_test_utils.h"
 #include "extensions/common/switches.h"
 #include "net/dns/mock_host_resolver.h"
@@ -255,8 +256,11 @@ IN_PROC_BROWSER_TEST_F(ExtensionResourceRequestPolicyTest,
   GURL nonaccessible_linked_resource(embedded_test_server()->GetURL(
       "/extensions/api_test/extension_resource_request_policy/"
       "web_accessible/nonaccessible_link_resource.html"));
+  // With PlzNavigate, the first DidStopLoading IPC is dropped because loading
+  // is delayed until the beforeunload handler ACK comes back.
   ui_test_utils::NavigateToURLBlockUntilNavigationsComplete(browser(),
-      nonaccessible_linked_resource, 2);
+      nonaccessible_linked_resource,
+      content::IsBrowserSideNavigationEnabled() ? 1 : 2);
   ASSERT_TRUE(content::ExecuteScriptAndExtractString(
       browser()->tab_strip_model()->GetActiveWebContents(),
       "window.domAutomationController.send(document.URL)",