Disable flaky test SendSideCongestionControllerTest/PacerQueueEncodeRatePushback.

TBR=srte@webrtc.org
NOTRY=TRUE

Bug: webrtc:9039
Change-Id: Ieb4cd437113e6291a326dff05dbcb96cbfdc06a6
Reviewed-on: https://webrtc-review.googlesource.com/63260
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22508}
diff --git a/modules/congestion_controller/rtp/send_side_congestion_controller_unittest.cc b/modules/congestion_controller/rtp/send_side_congestion_controller_unittest.cc
index ca93b41..ae9d1c4 100644
--- a/modules/congestion_controller/rtp/send_side_congestion_controller_unittest.cc
+++ b/modules/congestion_controller/rtp/send_side_congestion_controller_unittest.cc
@@ -472,7 +472,13 @@
   EXPECT_LT(*target_bitrate_bps_, bitrate_before_delay);
 }
 
-TEST_F(SendSideCongestionControllerTest, PacerQueueEncodeRatePushback) {
+// TODO(bugs.webrtc.org/9039): Enable when cause of flakyness found.
+#if defined(WEBRTC_WIN)
+#define MAYBE_PacerQueueEncodeRatePushback DISABLED_PacerQueueEncodeRatePushback
+#else
+#define MAYBE_PacerQueueEncodeRatePushback PacerQueueEncodeRatePushback
+#endif
+TEST_F(SendSideCongestionControllerTest, MAYBE_PacerQueueEncodeRatePushback) {
   ::webrtc::test::ScopedFieldTrials pushback_field_trial(
       "WebRTC-PacerPushbackExperiment/Enabled/");
   SetUp();