Move setup of base::test::ScopedFeatureList earlier, to avoid data race.

content/browser/top_document_isolation_browsertest.cc

Index: content/browser/top_document_isolation_browsertest.cc
diff --git a/content/browser/top_document_isolation_browsertest.cc b/content/browser/top_document_isolation_browsertest.cc
index 17caf7ae0c59c10d9c3ab948df735cedfb5d59af..be1fa6e4565e9c832525e88effca4441e07634fa 100644
--- a/content/browser/top_document_isolation_browsertest.cc
+++ b/content/browser/top_document_isolation_browsertest.cc
@@ -31,8 +31,12 @@ class TopDocumentIsolationTest : public ContentBrowserTest {
     return visualizer_.DepictFrameTree(node);
   }
 
-  void SetUpOnMainThread() override {
+  void SetUp() override {
     scoped_feature_list_.InitAndEnableFeature(features::kTopDocumentIsolation);
+    ContentBrowserTest::SetUp();
+  }
+
+  void SetUpOnMainThread() override {
     host_resolver()->AddRule("*", "127.0.0.1");
     SetupCrossSiteRedirector(embedded_test_server());
     ASSERT_TRUE(embedded_test_server()->Start());