Disable ProcessMemoryMetricsEmitterTest.FetchDuringTrace on Mac.

TBR=erikchen@chromium.org

Bug: 989810
Change-Id: I45c6ba5ddc575e8c5202ca32db5165169de1421b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994289Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#730132}

chrome/browser/metrics/process_memory_metrics_emitter_browsertest.cc

@@ -707,8 +707,9 @@ IN_PROC_BROWSER_TEST_F(ProcessMemoryMetricsEmitterTest,
 }
 #endif  // BUILDFLAG(ENABLE_EXTENSIONS)
 
-// TODO(crbug.com/989810): Re-enable on Win once not flaky.
-#if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || defined(OS_WIN)
+// TODO(crbug.com/989810): Re-enable on Win and Mac once not flaky.
+#if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || \
+    defined(OS_WIN) || defined(OS_MACOSX)
 #define MAYBE_FetchDuringTrace DISABLED_FetchDuringTrace
 #else
 #define MAYBE_FetchDuringTrace FetchDuringTrace