[sheriff] Disable the flaky test on linux.

AboutFlagsHistogramTest.CheckHistograms is flaky on linux.

TBR=asvitkine@chromium.org,ellyjones@chromium.org

Bug: 1141271
Change-Id: Ifbda96854d6b9658dd27c5d1f90f92e39347fd4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2491701
Commit-Queue: Hayato Ito <hayato@chromium.org>
Reviewed-by: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819699}

chrome/browser/about_flags_unittest.cc

@@ -151,7 +151,14 @@ class AboutFlagsHistogramTest : public ::testing::Test {
   }
 };
 
-TEST_F(AboutFlagsHistogramTest, CheckHistograms) {
+// http://crbug.com/1141271
+#if defined(OS_LINUX)
+#define MAYBE_CheckHistograms DISABLED_CheckHistograms
+#else
+#define MAYBE_CheckHistograms CheckHistograms
+#endif
+
+TEST_F(AboutFlagsHistogramTest, MAYBE_CheckHistograms) {
   base::Optional<base::HistogramEnumEntryMap> login_custom_flags =
       base::ReadEnumFromEnumsXml("LoginCustomFlags");
   ASSERT_TRUE(login_custom_flags)