disable MacAsyncSocketTest::TestConnectFailIPv6

BUG=webrtc:4738
R=kjellander@webrtc.org
TBR=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1179983003

Cr-Commit-Position: refs/heads/master@{#9439}
diff --git a/webrtc/base/macsocketserver_unittest.cc b/webrtc/base/macsocketserver_unittest.cc
index e98be91..97732d7 100644
--- a/webrtc/base/macsocketserver_unittest.cc
+++ b/webrtc/base/macsocketserver_unittest.cc
@@ -123,7 +123,8 @@
   SocketTest::TestConnectFailIPv4();
 }
 
-TEST_F(MacAsyncSocketTest, TestConnectFailIPv6) {
+// Flaky. See webrtc:4738.
+TEST_F(MacAsyncSocketTest, DISABLED_TestConnectFailIPv6) {
   SocketTest::TestConnectFailIPv6();
 }