Disable FullStackTest/ScreenshareSlidesVP8_3TL_Simulcast on Windows

It's started flaking.

Bug: webrtc:9840
Change-Id: Icc62c4715703f7e4d4f44ea11caf2f59351488d7
Reviewed-on: https://webrtc-review.googlesource.com/c/116520
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26166}
diff --git a/video/full_stack_tests.cc b/video/full_stack_tests.cc
index 765ace5..bceafe4 100644
--- a/video/full_stack_tests.cc
+++ b/video/full_stack_tests.cc
@@ -702,11 +702,13 @@
   fixture->RunWithAnalyzer(screenshare);
 }
 
-// TODO(bugs.webrtc.org/9840): Investigate why is this test flaky on MAC.
 #if !defined(WEBRTC_MAC)
+// All the tests using this constant are disabled on Mac.
 const char kScreenshareSimulcastExperiment[] =
     "WebRTC-SimulcastScreenshare/Enabled/";
 
+// TODO(bugs.webrtc.org/9840): Investigate why is this test flaky on Win/Mac.
+#if !defined(WEBRTC_WIN)
 TEST(FullStackTest, ScreenshareSlidesVP8_3TL_Simulcast) {
   test::ScopedFieldTrials field_trial(
       AppendFieldTrials(kScreenshareSimulcastExperiment));
@@ -736,6 +738,7 @@
       false};
   fixture->RunWithAnalyzer(screenshare);
 }
+#endif  // !defined(WEBRTC_WIN)
 #endif  // !defined(WEBRTC_MAC)
 
 TEST(FullStackTest, ScreenshareSlidesVP8_2TL_Scroll) {