Do not spawn a thread in browser/interactive ui tests before spawning sandbox host process

net/test/embedded_test_server/embedded_test_server.cc

Index: net/test/embedded_test_server/embedded_test_server.cc
diff --git a/net/test/embedded_test_server/embedded_test_server.cc b/net/test/embedded_test_server/embedded_test_server.cc
index 3d246d1a820588adb19cb8698fc60a6e56aa7db8..c7cf1efa7fff34c4b822fcb0d68ff6cb3a2d10dc 100644
--- a/net/test/embedded_test_server/embedded_test_server.cc
+++ b/net/test/embedded_test_server/embedded_test_server.cc
@@ -99,6 +99,10 @@ HttpListenSocket::~HttpListenSocket() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
+void HttpListenSocket::DetachFromThread() {
+  thread_checker_.DetachFromThread();
+}
+
 EmbeddedTestServer::EmbeddedTestServer()
     : port_(-1),
       weak_factory_(this) {
@@ -114,21 +118,31 @@ EmbeddedTestServer::~EmbeddedTestServer() {
 }
 
 bool EmbeddedTestServer::InitializeAndWaitUntilReady() {
-  base::Thread::Options thread_options;
-  thread_options.message_loop_type = base::MessageLoop::TYPE_IO;
-  io_thread_.reset(new base::Thread("EmbeddedTestServer io thread"));
-  CHECK(io_thread_->StartWithOptions(thread_options));
-
+  StartThread();
   DCHECK(thread_checker_.CalledOnValidThread());
 
   if (!PostTaskToIOThreadAndWait(base::Bind(
           &EmbeddedTestServer::InitializeOnIOThread, base::Unretained(this)))) {
     return false;
   }
-
   return Started() && base_url_.is_valid();
 }
 
+void EmbeddedTestServer::StartThread() {
+  DCHECK(!io_thread_.get());
+  base::Thread::Options thread_options;
+  thread_options.message_loop_type = base::MessageLoop::TYPE_IO;
+  io_thread_.reset(new base::Thread("EmbeddedTestServer io thread"));
+  CHECK(io_thread_->StartWithOptions(thread_options));
+}
+
+void EmbeddedTestServer::StopThread() {
+  io_thread_->Stop();
+  io_thread_.reset();
+  thread_checker_.DetachFromThread();
+  listen_socket_->DetachFromThread();
+}
+
 bool EmbeddedTestServer::ShutdownAndWaitUntilComplete() {
   DCHECK(thread_checker_.CalledOnValidThread());