Fix race in SecurityExploitBrowserTest and SiteIsolationStatsGathererBrowserTest

content/child/site_isolation_stats_gatherer_browsertest.cc

Index: content/child/site_isolation_stats_gatherer_browsertest.cc
diff --git a/content/child/site_isolation_stats_gatherer_browsertest.cc b/content/child/site_isolation_stats_gatherer_browsertest.cc
index 852ddabe0454d9294114a97f7658e068699aa16d..9150a97a046ab302d62251d72f585819fb6dc4ae 100644
--- a/content/child/site_isolation_stats_gatherer_browsertest.cc
+++ b/content/child/site_isolation_stats_gatherer_browsertest.cc
@@ -29,7 +29,12 @@ class SiteIsolationStatsGathererBrowserTest : public ContentBrowserTest {
   ~SiteIsolationStatsGathererBrowserTest() override {}
 
   void SetUpCommandLine(base::CommandLine* command_line) override {
-    ASSERT_TRUE(embedded_test_server()->Start());
+    // EmbeddedTestServer::InitializeAndListen() initializes its |base_url_|
+    // which is required below. This cannot invoke Start() however as that kicks
+    // off the "EmbeddedTestServer IO Thread" which then races with
+    // initialization in ContentBrowserTest::SetUp(), http://crbug.com/674545.
+    ASSERT_TRUE(embedded_test_server()->InitializeAndListen());
+
     // Add a host resolver rule to map all outgoing requests to the test server.
     // This allows us to use "real" hostnames in URLs, which we can use to
     // create arbitrary SiteInstances.
@@ -43,6 +48,12 @@ class SiteIsolationStatsGathererBrowserTest : public ContentBrowserTest {
     command_line->AppendSwitch(switches::kDisableWebSecurity);
   }
 
+  void SetUpOnMainThread() override {
+    // Complete the manual Start() after ContentBrowserTest's own
+    // initialization, ref. comment on InitializeAndListen() above.
+    embedded_test_server()->StartAcceptingConnections();
+  }
+
   void InspectHistograms(const base::HistogramTester& histograms,
                          bool should_be_blocked,
                          const std::string& resource_name) {