Avoid changing enabled features while the browser is already running.

chrome/browser/task_manager/providers/web_contents/subframe_task_browsertest.cc

Index: chrome/browser/task_manager/providers/web_contents/subframe_task_browsertest.cc
diff --git a/chrome/browser/task_manager/providers/web_contents/subframe_task_browsertest.cc b/chrome/browser/task_manager/providers/web_contents/subframe_task_browsertest.cc
index c52dae5fc3ce29af63b460ce5469b7f883de5fee..1cc87bfac65441aeac65b5db0f056bc50f15492f 100644
--- a/chrome/browser/task_manager/providers/web_contents/subframe_task_browsertest.cc
+++ b/chrome/browser/task_manager/providers/web_contents/subframe_task_browsertest.cc
@@ -206,8 +206,12 @@ class SubframeTaskTDIBrowserTest : public InProcessBrowserTest {
   SubframeTaskTDIBrowserTest() {}
   ~SubframeTaskTDIBrowserTest() override {}
 
-  void SetUpOnMainThread() override {
+  void SetUp() override {
     scoped_feature_list_.InitAndEnableFeature(features::kTopDocumentIsolation);
+    InProcessBrowserTest::SetUp();
+  }
+
+  void SetUpOnMainThread() override {
     host_resolver()->AddRule("*", "127.0.0.1");
     ASSERT_TRUE(embedded_test_server()->InitializeAndListen());
     content::SetupCrossSiteRedirector(embedded_test_server());