Disable a couple flaky RampUpTest tests on Mac.

Specifically, UpDownUpAudioVideoTransportSequenceNumberRtx
and AudioTransportSequenceNumber.

TBR=stefan@webrtc.org

Bug: webrtc:8878
Change-Id: I24ad65dc56068bb01c53d97511faadc22bd13c31
Reviewed-on: https://webrtc-review.googlesource.com/52161
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21992}
diff --git a/call/rampup_tests.cc b/call/rampup_tests.cc
index d035416..3a85214 100644
--- a/call/rampup_tests.cc
+++ b/call/rampup_tests.cc
@@ -598,7 +598,15 @@
   RunBaseTest(&test);
 }
 
-TEST_F(RampUpTest, UpDownUpAudioVideoTransportSequenceNumberRtx) {
+// TODO(bugs.webrtc.org/8878)
+#if defined(WEBRTC_MAC)
+#define MAYBE_UpDownUpAudioVideoTransportSequenceNumberRtx \
+  DISABLED_UpDownUpAudioVideoTransportSequenceNumberRtx
+#else
+#define MAYBE_UpDownUpAudioVideoTransportSequenceNumberRtx \
+  UpDownUpAudioVideoTransportSequenceNumberRtx
+#endif
+TEST_F(RampUpTest, MAYBE_UpDownUpAudioVideoTransportSequenceNumberRtx) {
   std::vector<int> loss_rates = {0, 0, 0, 0};
   RampUpDownUpTester test(3, 1, 0, kStartBitrateBps,
                           RtpExtension::kTransportSequenceNumberUri, true,
@@ -650,7 +658,13 @@
   RunBaseTest(&test);
 }
 
-TEST_F(RampUpTest, AudioTransportSequenceNumber) {
+// TODO(bugs.webrtc.org/8878)
+#if defined(WEBRTC_MAC)
+#define MAYBE_AudioTransportSequenceNumber DISABLED_AudioTransportSequenceNumber
+#else
+#define MAYBE_AudioTransportSequenceNumber AudioTransportSequenceNumber
+#endif
+TEST_F(RampUpTest, MAYBE_AudioTransportSequenceNumber) {
   RampUpTester test(0, 1, 0, 300000, 10000,
                     RtpExtension::kTransportSequenceNumberUri, false, false,
                     false);