Ensure all content_browsertests call the host resolver in SetUpOnMainThread and not after.

content/test/browser_test_utils_browsertest.cc

Index: content/test/browser_test_utils_browsertest.cc
diff --git a/content/test/browser_test_utils_browsertest.cc b/content/test/browser_test_utils_browsertest.cc
index 9303cd3d9a1d781e7e78efc07a9ca69bb112b11a..a59ef49de9014cdf3adc9f427e268b7803d65266 100644
--- a/content/test/browser_test_utils_browsertest.cc
+++ b/content/test/browser_test_utils_browsertest.cc
@@ -47,12 +47,16 @@ class NavigationObserver: public WebContentsObserver {
 class CrossSiteRedirectorBrowserTest : public ContentBrowserTest {
  public:
   CrossSiteRedirectorBrowserTest() {}
+
+  void SetUpOnMainThread() override {
+    // Map all hosts to localhost and setup the EmbeddedTestServer for
+    // redirects.
+    host_resolver()->AddRule("*", "127.0.0.1");
+  }
 };
 
 IN_PROC_BROWSER_TEST_F(CrossSiteRedirectorBrowserTest,
                        VerifyCrossSiteRedirectURL) {
-  // Map all hosts to localhost and setup the EmbeddedTestServer for redirects.
-  host_resolver()->AddRule("*", "127.0.0.1");
   SetupCrossSiteRedirector(embedded_test_server());
   ASSERT_TRUE(embedded_test_server()->Start());