[Sheriff] Disable OmniboxPopupContentsViewTest.EmitAccessibilityEvents on Mac

TBR=jdonnelly@chromium.org

Bug: 11401539
Change-Id: Ia9963196b784a1e1b923d488af722df2bff000de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485440Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818577}

chrome/browser/ui/views/omnibox/omnibox_popup_contents_view_browsertest.cc

@@ -393,7 +393,14 @@ IN_PROC_BROWSER_TEST_F(OmniboxPopupContentsViewTest,
   EXPECT_EQ(color_before_focus, omnibox_view()->GetBackgroundColor());
 }
 
-IN_PROC_BROWSER_TEST_F(OmniboxPopupContentsViewTest, EmitAccessibilityEvents) {
+// Flaky on Mac: https://crbug.com/1140153.
+#if defined(OS_MAC)
+#define MAYBE_EmitAccessibilityEvents DISABLED_EmitAccessibilityEvents
+#else
+#define MAYBE_EmitAccessibilityEvents EmitAccessibilityEvents
+#endif
+IN_PROC_BROWSER_TEST_F(OmniboxPopupContentsViewTest,
+                       MAYBE_EmitAccessibilityEvents) {
   // Creation and population of the popup should not result in a text/name
   // change accessibility event.
   TestAXEventObserver observer;