Enable Site Isolation for Extensions.

extensions/browser/guest_view/web_view/web_view_apitest.cc

Index: extensions/browser/guest_view/web_view/web_view_apitest.cc
diff --git a/extensions/browser/guest_view/web_view/web_view_apitest.cc b/extensions/browser/guest_view/web_view/web_view_apitest.cc
index babdbf5597cb497060ea6b5208ed8b29497577b2..2037f846d605fc8aae80a51503c5120c61ec63e1 100644
--- a/extensions/browser/guest_view/web_view/web_view_apitest.cc
+++ b/extensions/browser/guest_view/web_view/web_view_apitest.cc
@@ -193,10 +193,7 @@ void WebViewAPITest::SetUpOnMainThread() {
   TestGetConfigFunction::set_test_config_state(&test_config_);
   base::FilePath test_data_dir;
   test_config_.SetInteger(kTestWebSocketPort, 0);
-  bool isolate_extensions = base::CommandLine::ForCurrentProcess()->HasSwitch(
-                                ::switches::kSitePerProcess) ||
-                            base::CommandLine::ForCurrentProcess()->HasSwitch(
-                                extensions::switches::kIsolateExtensions);
+  bool isolate_extensions = true;
   test_config_.SetBoolean(kIsolateExtensions, isolate_extensions);
 }