Retry until EmbeddedTestServer is listening on a valid port.

The net stack will not send HTTP requests to a specific set of
blacklisted ports, but the OS may assign one of	those ports to
the EmbeddedTestServer.  This was causing spurious net_unittests
failures on iOS when it happened.  This CL modifies the
EmbeddedTestServer to retry until it is assigned a
non-blacklisted port.

BUG=607630

Review-Url: https://codereview.chromium.org/2562893002
Cr-Commit-Position: refs/heads/master@{#437602}

net/test/embedded_test_server/embedded_test_server.cc

@@ -23,6 +23,7 @@
 #include "crypto/rsa_private_key.h"
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
+#include "net/base/port_util.h"
 #include "net/cert/pem_tokenizer.h"
 #include "net/cert/test_root_certs.h"
 #include "net/log/net_log_source.h"
@@ -92,6 +93,18 @@ bool EmbeddedTestServer::Start() {
 bool EmbeddedTestServer::InitializeAndListen() {
   DCHECK(!Started());
 
+  const int max_tries = 5;
+  int num_tries = 0;
+  bool is_valid_port = false;
+
+  do {
+    if (++num_tries > max_tries) {
+      LOG(ERROR) << "Failed to listen on a valid port after " << max_tries
+                 << " attempts.";
+      listen_socket_.reset();
+      return false;
+    }
+
     listen_socket_.reset(new TCPServerSocket(nullptr, NetLogSource()));
 
     int result = listen_socket_->ListenWithAddressAndPort("127.0.0.1", 0, 10);
@@ -108,6 +121,11 @@ bool EmbeddedTestServer::InitializeAndListen() {
       return false;
     }
 
+    port_ = local_endpoint_.port();
+    is_valid_port |= net::IsPortAllowedForScheme(
+        port_, is_using_ssl_ ? url::kHttpsScheme : url::kHttpScheme);
+  } while (!is_valid_port);
+
   if (is_using_ssl_) {
     base_url_ = GURL("https://" + local_endpoint_.ToString());
     if (cert_ == CERT_MISMATCHED_NAME || cert_ == CERT_COMMON_NAME_IS_DOMAIN) {
@@ -117,7 +135,6 @@ bool EmbeddedTestServer::InitializeAndListen() {
   } else {
     base_url_ = GURL("http://" + local_endpoint_.ToString());
   }
-  port_ = local_endpoint_.port();
 
   listen_socket_->DetachFromThread();