[Sheriff][Looksalikes] Disable Idn_SiteEngagement_Match for Mac OS

The same test was previously crashing over all platforms, which
led to disabling it over all of them. However, the problem now
with Mac OS. Thus, disabling it only for Mac OS.
See: https://ci.chromium.org/p/chromium/builders/ci/Mac10.13%20Tests%20%28dbg%29/19839

TBR=jdeblasio@chromium.org

Bug: chromium:1122078
Change-Id: I773ffb8ce9dc8f751c90010979b0e4dcbf89c5a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2376855Reviewed-by: Amr Aboelkher <amraboelkher@google.com>
Commit-Queue: Amr Aboelkher <amraboelkher@google.com>
Cr-Commit-Position: refs/heads/master@{#801863}

chrome/browser/lookalikes/lookalike_url_navigation_throttle_browsertest.cc

@@ -9,6 +9,7 @@
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/scoped_feature_list.h"
 #include "base/test/simple_test_clock.h"
+#include "build/build_config.h"
 #include "chrome/browser/engagement/site_engagement_score.h"
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/history/history_service_factory.h"
@@ -768,12 +769,19 @@ IN_PROC_BROWSER_TEST_P(LookalikeUrlNavigationThrottleBrowserTest,
                            custom_test_server.GetURL("googlé.com", "/"));
 }
 
+// TODO(https://crbug.com/1122078): Enable test when MacOS flake is fixed.
+#if defined(OS_MAC)
+#define MAYBE_Idn_SiteEngagement_Match DISABLED_Idn_SiteEngagement_Match
+#else
+#define MAYBE_Idn_SiteEngagement_Match Idn_SiteEngagement_Match
+#endif
+
 // Navigate to a domain whose visual representation looks like a domain with a
 // site engagement score above a certain threshold. This should record metrics.
 // It should also show lookalike warning interstitial if configured via
 // a feature param.
 IN_PROC_BROWSER_TEST_P(LookalikeUrlNavigationThrottleBrowserTest,
-                       Idn_SiteEngagement_Match) {
+                       MAYBE_Idn_SiteEngagement_Match) {
   const char* const kEngagedSites[] = {
       "http://site1.com", "http://www.site2.com", "http://sité3.com",
       "http://www.sité4.com"};