Disable a flaky AutoplayMetricsBrowserTest on more platforms.

AutoplayMetricsBrowserTest.RecordAutoplayAttemptUkm is failing on
non-Windows platforms as well.

Bug: 1101841
Change-Id: I641bcbadd9e3ad52bcc4a5bc39bac08a4dbf34e5
Tbr: tommi@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2357619Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798383}

chrome/browser/media/autoplay_metrics_browsertest.cc

@@ -64,8 +64,8 @@ class AutoplayMetricsBrowserTest : public InProcessBrowserTest {
   }
 };
 
-// Flaky on Windows. https://crbug.com/1101841
-#if defined(OS_WIN)
+// Flaky on various platforms. https://crbug.com/1101841
+#if defined(OS_WIN) || defined(OS_LINUX) || defined(OS_CHROMEOS)
 #define MAYBE_RecordAutoplayAttemptUkm DISABLED_RecordAutoplayAttemptUkm
 #else
 #define MAYBE_RecordAutoplayAttemptUkm RecordAutoplayAttemptUkm