[Sheriff] Disable ExtensionContextMenuLazyTest.IncognitoSplit

Test is flaky on Mac and Windows. Disable it on those platforms.

Bug: 1035062
Tbr: dbertoni@chromium.org
Notry: True
Change-Id: Id556b0cde7e9ca26a3b4b3e0fac244f794427010
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1974577Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726101}

chrome/browser/extensions/extension_context_menu_browsertest.cc

@@ -892,8 +892,15 @@ IN_PROC_BROWSER_TEST_P(ExtensionContextMenuLazyTest, EventPage) {
   ASSERT_TRUE(listener.WaitUntilSatisfied());
 }
 
+// Flaky on Mac and Windows. https://crbug.com/1035062
+#if defined(OS_MACOSX) || defined(OS_WIN)
+#define MAYBE_IncognitoSplitContextMenuCount \
+  DISABLED_IncognitoSplitContextMenuCount
+#else
+#define MAYBE_IncognitoSplitContextMenuCount IncognitoSplitContextMenuCount
+#endif
 IN_PROC_BROWSER_TEST_P(ExtensionContextMenuLazyTest,
-                       IncognitoSplitContextMenuCount) {
+                       MAYBE_IncognitoSplitContextMenuCount) {
   // TODO(crbug.com/939664): Not yet implemented.
   if (GetParam() == ContextType::kServiceWorker)
     return;